Ion kinetic energy spectrometry

107 ION KI&xErIC ENERGYSPIzcIRC6lElRY

Department of Chemistry. (Received

ion kinetic

it_

Special

is given

underlying

of the paper discuss

resolution

energy spectrometqz

becomes broad ranging

ez&asis

and the philosophy

sections lar

of

hc3iia new technique

found for tation

Useful

data acquisition

47907

are also

performance

release

and for energy change in collision

to various

The application

The iast into various

and

ion kinetic reac-

of translational

processes

_

energy

that are not accompa-

of ion kinetic

energy spectrmetry

are e_xplored and likely

future

developments

discussed_

quarter fields

has seen the development of mass _spectrometry

century

from those of

different

abundances of

the nuclides-

mea of vision

seem to have gravitated

that they tiere also

its

early

vividly

their

illustrated Albert

beginnings

for

that Iehich included

Ikmpster

Kingdom, separates

e_xperiuental ists _

the early

figure

ideas mst

go_

in the United States researchers

the succession

in that

equipment and to do last

the

year

links riith

in Buxton,

uho in 1915 MS a post-doctoral

the senior

And still,

lihen it and relative

been fortuuate

For one of us,

in a conversation

f3gle

ratios

it and even more fortunate

to build

ideas_

J_ J- Thomson, the father

4xm so much credit

has almys

towrds

people able

dcveloP

FngIand with Professor uudcr the great

The subject

practical

to further

the past mre

mass and angu-

and ion/surface

scn-ed only as a method of measuring the mass to charge

cxperincnts

Important

ion detection

measurement of

for distributions

problems in analysis

the subject

and crethods of

ion/molecule

Peak shapes are analyxd

nied by frmgmxtation.

lnade to it_

cannot alh~ys be optimized

The basic

t ions _

are

of the instrumen-

in terms of energy,

scanning procedures assessed_

as new applications

modifications

encx-5Jyis used to study unimolecular,

United

Indiana

is used to illus-

to a description

and show that the requirements

siQultur_eously_

of

Nest Lafayette,

2 May 1975)

The develoigcnt trate

Purdue University,

fellow

of mass spectrometry Only a single

to

generation,

and F_ K_ _&ton

in the

of today from the earliest

of outst‘anding mass spectro-

In the past several

sCopistr

is 5trong.

journals

devoted to 3rticks

aml the preseut aPF==d bs mcbed rctfl-csKmt. Fr;lilEifin*s

Dr_

ticularly scvmat also

closely

related

tmmctry couccrnrl

issue

on :he

cnsrgy pwtitiating

the dccoqusition

1atjon

probable

in most casczz,

rotat iomt Wh enem

uorc

this

about

tk

than k-hau the &t-e

of

aetastsblc

energy

this

fS,til

pczk;

zuxi zany

rclcasc

is

dcfkcticm

ins- ~nemnts

to cstimatc

cocrgics the wtbad

wcrc

frqpcnt

above,

this

[ZO]_

[a]

cncrgy

excess

(in

energy,

cncrsy

oi

trans-

ribmtiomxf

either

of

[lS.191

ions

or

tnnslcltional

same 20 parS

to be diet to this ha-c

the ion for

the

particukirly

rclcva3t

results

of

using

cncrgy

netho&

from the detailed

of but

Jctai led_

spctroThey luvc shape

of

the

Like the other methods

in scnsitivitv

fzugwntxtion

1%

IlO,lIl_

ion fn_paeut~tion_

in the mass qnxtrtm.

moict_u fornzd during

dis-

could

Imvc been obtained

gc netax

the rcxctions

magnetic

the sprmd

have mad& use of 3 timC-of-flight of

ions

rcsuitznt

mass peaks

bcm used to investigptc U_wful

of

ions formod Kith The

SOUTCC-

with

in instmces

masurcaaznts

the trmsl~tiomf

a_g0-

transla-

been conccrncd

Kith the study of

is _zorPeehfutliaitcd

and rc&ircs

fern an ztpprociable

that frxtion

ion_

irtrcstipting

Encrg- analy5is

this

kTittcn

lc or 3s axuratc

crass of the decoqosing

Another xcthod of for

wzrc

Kitbin

iug the cncrgctics

the enm-gy profile

the ucutr;il of the

a5 versati

invcstigat

due to

described

him

out

Qthcr cwfy

cancc&

encrs*

magnitude of

tk

and cotmrkcrs

dcdmxd

In con-

35 is the cr)5rc of the &composition

ucthods Ih;rvc also

is not

for

peaks

rule

5f2asuTcapM ts

in the ion bczm [12-l?]_

Fmnttin

reactions_

be px-ckainultty

uwds

for c_xmplc_

of translationA

tkflcction

uetcr

Kill

occurrmcc

tort ion of the uaucutu4t distribution used

energy spcc-

an activation

inrolve~

hmm bcwn shorn

early

iargc,

carrying ttm charps, release

;mJ Khich is

book Kith Ur_ F. H, Field

pczk Kidth aad cflcr’gy rctC%~se 17,5,9j,

rck3ting

broztd ~1t-e~

of ion kinetic

fx3guents

tmuld

par-

h3s been profound.

iqxx-t;mt

in uoimkcular

definitely

W+ cannot

is non know

rclcuc

ahem

rcwztions

ideas,

cscitatial-”

?bc widths tional

ttnt

hwc

that Dr- J_ L. Franklin

the mast

hc b-tote in his classic of the mtccule-ion

[1,2,3]

thought in this

to one of the appliwtions

question

it w

ionic of

onz= which is zmng

addition to the mdotheriaicity~ tk mile

of

of the

of our current

det~lojmmt

has hem a leader

issues

figures

is a rariudcr

the cncrg2tics

k i&rs

km&ark

sidering this “if

journal

38 they affect

special

honoring outsttiing

infhxence

Thx-oughatt his careor

years

energy

spreads

ctzploys the il3ly dctm-

is hascd upon ion retardation

[21])

the lokw

109

kinetic

energy coqonents

the potential

of the beam being

of the repelling

electrode

discrinunated

is increased.

aboutleVhasbeenreported[22]inabeam is, to

as yet, solving

little

information

regarding

problems-

d sector

scpntcs

the criers

profile

been used to derive

cnewctic

the application rtrrgnetic field

to its

a scale

ratio

if

cxxnentumto charge ratio to provide

the sxrss-to-charge

sector

is readily

as an energy analyzer

achieved-

been obtained

Ibis

recently

paper uill

spanning physical, siue

revi-

organic

of the subject

hark h-ill ;Ittcqt uental

additions

by atrerapting thinhing

of 1 in lo4

results

that have

hay and Cl1

in-

energy spectlometry

this

research

=

Ekcausc a coqx-ehenb-ear [26]

by discussing

the inrpact that current

uses an

several

the present

recent

instru-

zt Purdue University wrk

and

nary have on future

and dcvCIo_~ts,

in closely

instnraent,

related

Ihe originial

energy spectr~etr?_

f29-31]_

has intended to

of high

fulfill

instruncnt

side diameter) ; the pmping to those associated

large

sysim

due to Professor

and to be capable

for netrist&le that 131dc it far-se site five

t.-ith sample-handling,

or as It

ions_

is

has been concerned,

cross-section

included

cqwriwnts

high amass resolution

idc;ls; it \stl_sof

\
role

l\hich our rcscarch

had n;my features

rcsem-ch

KIS %I) ; the xu-c-guide

giving

began

I?Ml-2 uas~ spectrometer_ features

a dual

measurements

Gth

at Purdue began in

laboratories

_All of the car?-

m;my design

35 an irwtnraent scmsiziuity

capability

deseloprrtcnt of ncx

other

with a flitachi/Pcrkin-frlmcr

of being used either only the fatter

areas

\
I-_ K_ WLaffcrty, one capable

ion kinetic

At about the silsipc time sevxal

here IXWC pcrfomed

addition

in this

chemistry.

is being published

to cos&plcar_?ntthis

lhc dcrclopmcnt of

This

and analytical

in

is known.

typical

sector

ion kinetic

and the aims of recent

to assess

1963 [27,28]. working

of

calibrated

in our laboratory

illustrate

l

clude e_xaqrlcs of the applications

it has

and an energy resolution

usin=.* an electric

field

using a nono-

ratio

a scale

ratio

The wtthod Khich has been used esclusively electric

be used to

-Although this

of rrus-to-charge

he;tn and cq- he used stilarly

cncqgy-to-chxgc

as

of

of the detector nay also

of an ion beast [23-251,

an ion beax3 according

cowonly

first

of energy 10.000 eV but there

specific

investigate

against

A resolution

ideal

(typically oil

for

the

(the path length

diffusion resulting

T-5 cm outpumps in in the

poSsihilitv S of good differential ptqinp hetwen all the various of the vacuLB?L system; the four slits at the source and collector,

regions at the

110

sector region L-ould energy focus between the sectors and in the pre-electric all be adjusted in the y-direction and also rotated slightly as ~11 as being variable

in width-

In additiOn,the

slits

together

with a s0urce working at 1 rit4total

Zesmb

?kSmO&?z

In the past six years, ing to rmtastable many changes. buitz

sane of the nw

incorporating

ideas

more convenient

RWf-2 continues

the

the original

to be an instrment

the rmdifications

ES&C to it over the years

the

new instrraaent)

always present

their

in research

wrk

sequence of ewmts

sufficient

larosrledge or preparation

ca@etely

the results

aid

BIEdl effort

it

WiIl

progress

without

take a _Grilar

course

kinds of c_xperiments that

perfOrmed under Ices

in assessing likely

hops valwble

he shall

also

alleys

paper but try to_usc

there

is essential

is arc

to per-

a new idea and

conditionsis likely

Hopeful Iy, to be and how

to consunke in the long term hut inevitably, and significance

knys

of the ueas-

These are the e*xperiraents that keep the enthusiasa of a research

ulxments-

group high but they must be limited both in number and duration term potential haever,

in-

believe the abject

to test

the idea

equal

blind

in the present

it

than ideal

ilEprOving the speerl, a ccuracy

be seen of

giving

because of

tJhi the many unproductive

of these is the quick experGxmt

is

fore-

the

underlying

the cOntinuOus,

We halve, thrOughOut, taken the view that

distinct

is inevitably

at

in which researchers

that have to be repeated

the path along hhich m

to illustrate

fornt, The first this

he shall

developing-

am-mtly

is

(and IMW a1s0 those being made

place ax)re ekxphasis upon the in35 ruaentatiOn_

our research tm

of wrking

and upon the wy

that constitutes

to the nany e_xperiwnts

that are explored_

it

in same rspeccs,

to be due to the philosophy

in a amnner that -hasires

prwainencc

will

was based on the

with the Mi-2,

in a previous paper 132) w camentecI on the irn-

.

portance of serenJipit:r logical

its design

capable

and -this we believe

pertain-

geometry has been

to use and more p0herful

front of reseaxh to

reversed

and because

interests

instrument has undergone

krowledge of more than tx0 y3zaz-s’ research

understandably Rut

emission gave go0d sensitivity.

as the range of our research

ions has expanded,

A new instnsucnt

to test

acLmated

km-e 1 an long and this,

of the rcsearxzh is to be reaiited-

individual

cimxastances

sighting

of proceedin?pto the next s00n as possiblenary results

expertits

he carriedI on too long_

of this The careful

sta_ge of experimentation

if

the long-

Nore islportantly, kind should nOt uncier any and often

tedious

nest be -leted

task as

Yhis second kind of e_xperiraent based upon the prelirsi-

should always be performed with a view to contributing

town-ck

II1

future

e_sperimen tsandofnaintainingthesta.ndardofperformanceofthe

instruaient. Permanent and often irreversible changes will be made to the instrwaentationat this stage and it is vital that they take account of convenience of operation of the equimnt as well as the level of accuracy and of versatility that they give. This disciplined approach nust then, ideally, be continwd until the experinents are completed and written up before the next idea is developed. A corollary of the above approach is to ----maintain the inst rument in the best possible xxorkingorder at all times. Minor troubles must be noted

and dealt with, otherw5se a slow but inevitable

deterioration in the quality of the research will occur. The nu&er of e_xpensivespectrometers "rhatcan be justified depends upon the number of r~-orth&ileideas that can be followed up according to the standards put fomard above. Several projects will, inevitably, need to be continued on one instrunent over any particular period to justify its cost and there is thus continuous pressure to build a verv versatile piece of equipr;entcapable of use over a wide range of topics. Great be

exercised

to avoid c~ranises

care must

in design aimed at meeting the con-

flicting requirenrnts of different experiments. The important research aims must he

identified and the equipnent designed to meet these. Other,

snrstbe rejected if they are in conflict with these. subsidiary, air-as These considerations vi11 be illustrated by the research examples given hclow in the various fields of research described. Basically, the esperkents perfomed

in our laboratory are

COnCerner!

with metastable ions. W are interested primarily in their fra=,anentation reactions and in the masses, structures and internal energies of the products. Ke are interested, too, in the transition state itself and in the nechanilss, rates and energetics of reactions. A parallel interest is in reactions induced by collision processes with gases and riithsurfaces. These latter interests have led to experiraentsdesigned to investigate cncrgy transfer mechanisrixs and the general topic of inelastic collisions. In both untilccular and collision-inducedreactions the conversion of internal energy into translational energy \shichleads to the broadening of netastable pgaks and of those resulting frum collisions, is of major interest. The reveme processes. in &ich translational energy is converted into internal energy are often collision studicri. slighly

Mt

all

modified

of these subjects mass spectraneters.

hare been modified

to such an extent

are ideally

induced and are also suited

nor even by those that we describe

for

study with

instruments

that

them as kinetic

5fcwetiElesh~ha~~pel-fOrmcJ

enel-gyzpxtrweteIs.

scouting@SperiJmts

on

suchsubjects,eventRoughtheSnst

rumntation available is not ideal and in sme cases have concluded that the infomation gSned is only at the borderlinfzofourinterestsso thatnoins tmzcenf mdifications are justified. In othercases,amCrethc resultsof preI~narywwksuggcst that important resuIts appliclble to our general interests in analytiml, physical-organic and theoretical &cm&try

my

be possible,

pmmmnt

instnmcnt additions

mdllPodifiutionshavebeenmdeTheseqwz~~eofemnts tbatzuztybe inuolucdanbcillustra~cd

witha

particular example and with a diagram that mzps the entire mnge of optionsF~gurcl~~~ternati~~3~~~of1nesiirleaorigi~ting in thebroad

CHOICE : OF INSTAUYENT

RANGE

0’:

IR3TRUYENTS

1

AVAILABLE

f

\

11 NEW

INSTRt

FmJRE I_ Illustration of the manner in which Seas say-become incorpomted inthe re~e3rch being perfozaed, An idea is checkd against the broad field of interest of the research group, If it falls within this, it is assessed for quaIity and for its @m-tance. Only if it is thought to be of highest qmlit)r will research mney be sought to enlarge the field of interest and buZldrtew equipment, IE it is cap&lc of developmznt on existing instruuzentsand effort is available, 3 choice of instmnzent ismade forthepreEixnixuxyexpemts. additional criteria being availability of instnment andthe amomS ofmuiiflcation needed, The results ofthepreliminaryexperimentsmayindiuteapermvEn t~kI.eofthenew rese;rrchand lead to peIx!SmSt Etrdificationof an ins-t.

field

of

intorest-

extrerw,

_Assoss;r#mt IXQ- lead to rejection

or at the other,

to the construction

of the idea at the one

of a coupletelp

new instrument.

In between these extrexaes the idea can lead to e_xperixnentation that arrayor rxry not require

inodification

nxnt 03 bc nodificd, other w~umzrcnt~ are nli

that will

prog-a= A particular

tion of

of inodification

necessa~-,

the ovemll

affect

course of such events KCS initiated the rcxwal

of tt-hich is still ion structure of

the subject

infomtion

idea wx~ld involve

As soon JS it h‘;ls decided

dctaiIcd

assesswnt

of

that

po~zibi I itics

tlscsc

Of the Jcr;ign, Iritihlc

to give

he useful

hutlId

others

to

debate-

-I-he ques-

reali3xI

procccrt

that

and imple-

its

this

capabilities

high]>- colliraated

k-as considered

scpmteiy;

instrumentation

of

ion beam of appreciable

led

r~xn-k- EXh

to modifications

too inconvenient

rejected_ IOli

a

in other directions,

some

wx-c thought to be either

Kith the uain purpo~c and SO wxc

new

at low translational

Cth

in VCI~- high energ)- resolution

current IJ- being crq>lo~-cd for studies

Even

an ion the

the construct ion of an entirely

had t0 bc rrudc of

its aiailitv

I-or oxa3ple, intensity

yields

through ncutrali=ation

instrument capzihic of dcl iverin, *I high ion currents c-ncr~gy_

species.

of concern to us so

It wrs imrediatcI>-

ions hf13 dcW2lOpCd_

racntation of this

ionized

one cltkron

pint

upon

of the research

of considerable

on this

effect

fron the realization

of

under1 ies uush of the chenistq

the idcz of so&in:= coilection

of just

its

instru-

is to be penaanent or not

efficienq

nothinK is kn~wr abOut the structure

in the cssc of benxnc ~trucfure

extent

-I-he particular

equiparent-

that can hc uadc and whether it

dccision.s

that atnost

the

of existing

or incom-

The instrument

cnerz>- ion/surface

is

react ions

i;z;l_ _?%3gv?sso-r- tilt? .%?sfxur!_~ In t!rc foIIouing topics

Sections

an attcsrzx is nde

JcIxxrdcd on the inzXnaxxrts

investigation is dividcrl

.and in turn hoI< the pursuit

has Icd to nalification into sub-sections

linked

to show how the rcwarch

of the instruatentstion_ by a particular

of a line

of

The subject

instruncntal

feature

or

cxperimcnt31 procedurcfil

.\I~ss and energ,- rcsoliltion -f!igh CIZSS resolution is a feature

5Ixxt romctcr~, interest gcoactry

but high cncr~y resolution

in our research,

-t rLux?nt-

In OI&Xis

of wxn>- ccwzwric;tl

arrmgxl

to

get

uhiclr i+ the feature

is not necessarily high

so tltit,

double-fbcus:sing

sensitivity

no lilatter &at

attainable at

high

of priraav

with the sarze in-

EXISS resolution

the translational

the

energy of the

114 ion within energy using

a narrm

resolution

:_2”, of the

come to the correct

necessarily

gecmctry,

ktminal

electric

the

it will

is thus,

Nicr-Johnson

the

range of follow

range,

sector

poor,

typical

final

double

by narrowing

of achieving

high enew

the ekctric

sector

resolution

[S;r).

At this

slit,

portant

resolution

the kam

s,pccih: of

problcas_

resolving

variations

cam of the order

the bea

the stabiBity

intensity

umst be capable containing

of being varied

ion)

bcm of the MI-2

rO_6 eV at 1% peak height for stability,

of the highest

662 used to mmitor a mftcr

ir

accuratc1y peak 5s se,

the electric it

this

ing voltage

mxor

to follm

fields.

ions

chvlges

a spread of of GkeV [ 2Sl_

mltase,

and the in these

to USC a meter capable

differential and the

the qpcctramtcr

slit

The main (stable

used_

is ncccssa~

The F3zithlcy 6-dial

of electric

of

that CI p-e-

that a source of

for e_xmsplc, cshibits

and in order

in enabling

with any ratio

k

at an ion accclerat

amI mxmu-c these voltages

important

supplp

impormrtce; with CI

means not only

but also

range must

3x-e scanned,

rrccur;lcy.

and

powr

With a Kidc B-slit,

raolution

miss spcctrrxfEtcr,

as the fields

ier-

slit_

in width,

to monitor thi?; voltage,

quantities

is usuz~lly mrc

bc such as to give ninirslet vari;ltion

only 3 VCT)’ small encr_~

magnet current

is not necess;tr)r when

and it

reason.

side of

lligh mass

is nccdcd and. that the energ?- resolving

only

In crdcr

on either

on the RMi-2)_

10-i”, are of secondary nust

sector

hut the only a~-

of the high mltagc

smc

for high energy

electric

to the

so as to minimize drift

pssin_p. through this

The requi remnt cisioee

uith

slit

Uhc specification

needs to he iraprovcJ for the

narrow B-slit

slits,

but usually

studicd

into

High mass resolution

is to narrow the slits

ion is king

a

that

is dispersed

is transmitted

focus_

the source and ES-slits

to open the sass

senritirity also

and cp.erg~)

can be achiewed riaultancously,

a knom single

cxmple,

ccmmcrciai instnmcn ts tramnit

the source and collector

(i-c_

The

energy of the ion be;ii;r through the slit

(direction

is achieved

focus.

To take a specific

an energy spectrum from k-hich a range of energies point of

mss

voltmeter

availability

Mdcl of such

to bc set up rapidly

Also,

and

h3vm _sa?_,a mctastablc

~~+~sureaent of the peak width to be n;lde

meter emblw

a very high accuracy_ The zchiewaent

of structure rartastable

adequate

resolution

in numerous sact3stable peak is show3 in Fip-c

fms been observed solution

of high eners

[35-37 1_ resolution-

A typic31 case of a coaposite

in ;I few cases uibntioml

1%~ the obscmation

alone does not suffice. angvar

peaks2.

There This

has ztllohpJ the observation rtructurc

of such StmCture,

is an aiditioml

enem

rtquiremcnt

fo1Ioh-s because the natural

line

of width

rc-

xa

:65

166

167

164

FIGURE 2,

A tyqGca1 canposite metastablc peak, that for loss of HCl from I,+dichlorobutane, plotted by scanning the accelerating voltage using the Hitachi RMf-2 mass spectrometer_ The abscissa is calibrated as a percentage of the accelerating voltage (H.V.) required to tranm it the stable ion beam, of a frqrrent

ion in the kinetic energy spectrum is givep by the range of

energies

it contains

that

range of angles

and this

ok-cr Khich the products

Although none of our instruments angular

resolution,

trxxaeter

and also

latter

device,

incorporated bhcn

and for another

SpCCtn

(ii)

in the MIKE spec-

(which are variable

by the voltage later,

to maximize

has only

plateau recently

in the

chamber_ been

reason at that _

are plotted at high energy resolution it is tacitly mass sepant

path is adequately

criminations

especially

is achieved

lengths

in the y-direction

which is described

rissumed th;lt no prior the night

in the slit

upon the

of fr-.-._gmentations are collectecI.

have been designed

a measure of collimation

[3S] by reduction

r-direction) This

in turn is dependent riirectly

are introduced

ion has occurred.

shielded

magnetically!

at the energy resolving

lhis

is not so unless

Otherwise slit

mass dis-

[39]_

Scanning procedures A rnjor

advantage of using

ion-kinetic-energ>-

spectrometry

arises

when

th-o of the fields are used in the experiment to characterize txo independent pxamctcrs

of the resction,

could be the mass-to-charge established

For exmqlc, ratios

by momentumanalysis

using

the ElIKE spectrometer,

of the reactant of the reactant

and product ion and kinetic

ions as energy

these

It6 of the product

;ur;rlysis tion

nomally

available

peaks is obscure.

is in contr;tJistinction

fmfa SITS spectn

fhcrc

the three rmin fields routinely

This

ion,

ilre a IxSzber of possible

crkctric

the &vantages clscxhere

~cctor

voltage,

al

[26,4OJ-

Fired magnet current

is the prefcrrcd

general 1~ axe [Ji]

of conwntional

si~ltaeously

nnintain

l?fV constant_

accelenting information

Iisting

prent

voltage

mew-

Information

is cun-cntly

becoming available

inst ruaxxts of Sicr-Johnson use.xI

em-

rcsoht

ion.

the pssibilities

NC &xi&d,

therefore,

tfic pcrfommcc

of ,Wttauch-fkrzz

gemetq-

done and the pcrfonfancc

drcrc

using an electric

interest

lies

detailed

infomtation

in detecting

not to duplicate

characterist

its

is no focal

is

illwtratcd

ohtaincd

for analytical encrgv

vith

per-

;1 variable

in terms of this

mn-k but

with an iwtru-

point.

This has

in Fig_ 3_

purposcr,

tmnsition reIcasc,

even in the ~~SSMX of ;I focal

The prfomunce

i&e,

the pcrfommcc

there

spxtro-

the attainable

[42,43!_

that could be obtained

of pks

9 particular

concerning

focusing

This

the ~Iiiif spxtro-

scan and with the CIE 21-1101 i\trff;luch-tkr~og

It can bc seaa that

instrwtcnt-

is obtaincrl

sector

cannotbeob-

is nevertheless

concerning

~~ctu;lily attained

S~MIUSa caerp;lri_son of the pattcm aeter

rang2 than disadvantage

of the linkcxl scan metbock

geanetry

with sJI’;uItztge to &prove

zo im-cstig~tc

~~ttkcr wnt

it

tolzage

wx~kness that

in any transition

number of double

fomance

CCUI be

sector

in such ;r B;INWX as to

over an M-cn g-cater

in me

ions

with an instant

scan and the further

gcumctry currently

ancl scaa,

has been shohn

It

YaJ electric

retc~se

in vich’ of the large

voltage

31 I the daughter

qaccics,

ausnet currcnt

fulip

B-slit

scan gcthd.

in a single

can be obtained

inrpoxxant to investigate of

\xdtagc

have been discussed

This “1inkcrl” scan has the obvious

;icccLcr;lting

of conventional

the high volt-

ion accclcrJting

the high wltage at fixed

concerning

taimxl direct I_vmeters

information

volltagc has to be k3ricd

in the conventimal

tlmt

if

r;trM

acthod and gives,

infomation

geamtry

S.C~

the

the accclcnting of this

of a singie

that sitilx

is by var)-ing

GM-2

voltzkgf at fixcrl

ccm-cnimr

from frqmmtation

recently arc

of scanning tha of

hag

but only a fe# arc used

the revcrseci geometry ,\1IKIfzq-aectnarctcr, scan-

sector

fomcd

the

and Ji_xw.fantagcs

ning of the ckctric tk

of ISFIII~of the

in any one instrument-

age at fised fully

in which the origin

in ax energy spcctraeter

the standard 8eettmxiof scanning a&

to the infornn-

point

are reported

rather

extrcfmly betmen

in detail

k*crc than useful

thccin in gaining informtion

the analqa-s-

clsmhcre

iJJI_

117

70

MIKES

42 43

71 05

41

99

I a4

se

T2

I

i

57

LINKED SCAN

Spectra

of

n-Heptanetmass

1001

FIGURE 3. Gxqarison of t IIC energy spectrum of the molecular ion (m/e 100) of n-hcptane obtained using the NIIilE spectrometer with that obtain& On an instrument of conventional geometry (CXXI-Zl-IlOB) by the linked scan techniqueThe figure sh0h-s the overall similarity of the spectra but it does not shah. .the peak shapes rchich are narrow in the linked scan but variously broxkncd in the NIE spectrum, E;inctic energy release information is not obtainable from the linked scan spectrum,

(iii) Data Acquisition Mast mass spectrometers behind ;1 resolving detector plete

split

simultaneously_

CIX 21-1lOB spectrometer array

or the relatively

detector

[451_

field

focus

[46]

detectors

It h-as considered

lie 2; in the fringe

on another

the magnetic field of channeltron,

instrument (c-g_

that all

photographic

the RMl-2)

plate

to record

perfoxnted using

the infolnltion

the wn-k

in the Mattauch-Ilerzog field

of the magnet, for the

necessary

raxxld lie

such as that pertaining vieh-ing device,

com-

of the channeltron

be made ar:Glsble

in lilrich the detector

phosphor and vidicon

located

that these devices

&andthat

the instrument that could most readily

c:?periment device

the applications

SUthough it I\‘;ISappreciated

in the abscncc of a magnetic :as

insensitive

&I e_xperiment recently

investigated

geometry the plane of double this

multiplier

that has the compensating advantage of being able

5pectra

best

employ electron

hell

to fit

the

outside

to the mounting

the design

of

v3cuum

118 psindou betumm the vidiccln and phosphor, cording

and processing

of signals

the mltages

and the sensitivity

be obtained

in a preiitairnry

cxperiucnt.

plane using

the arrangement shokn schematically-

The dcvicc

to be applied,

the re-

axii resolution

could

has fitted

in Fig_ 3,

in the focal

It ms

found

lxu?E a_ Imaging detcctctr f8ttcJ to ;I focai plane mass 5pectrcmfXcr (CEC-21-1108)_ The detector consists of a chameltron electron multiplier army across which there is a .oltage gradient, a phosphor, an optical vidicon caae= t-%cther with an aritktx and display unit, that at 10~ EE&I'LC~~Cfieldls to-charge

Iomx

the first

mperkent,

corresjmnding

a peak arising

40 per secomJ was repetitiwzly ratio

of

2 in 50 seconds,

r?qxuTed clse34tem

[SS),

an ;~rra~ detector

7hc

very weak

mentation reactions the army

detector

signals

it

-GO_

MS2

generally

ions of EISS-

of

In

ions of about

at a signal-to-noise

could be measured sim~lta-

Details

of the exxperiment ham? been a similar

mntnting

instnment,

encountered

in the study of the frag-

ions which prompted the investigation

led ta w~earczh into signal

It was fbund that the electmnicaIly the &IKE spectrometer

of arrival

is now intended to design

on the

of uzetastable have a

frcxa a rate

scanned and displayed ratio

of

was extremeI_v sensitive_

About 3 mass pe&s

nfzously at a mass-to-charge to fit

to the detection

than about 20, the detector

controllfxi

could not be triggered

scanning

repetitively

a”crqins

of

sy-stes=;-

system fitted

on

with sufficient

119

reptiucibilitg loot,

and that as spectra wxe collected,

resolution was being [47] in xkick the shafts of JXo 15-turn

A system has devised

helical

potentiometers wxe connected together and a slotted disk was

directly on one of the skafts. _& the helical potentiometers were sczmn& a fraction of the voltage from a stable pm%er supply 1~3s applied

mounted

directly to rhe sector plates_

Ey counting the number of slots passing a

fixed position, a computer could be used to set the position at rihich a scan

kas

started tiith high reproducibility,

Speed of sun

h;is controlled

by a motor and gtxwbox, the motor being supplied froze 3 frequency controlled SOlXCC-

In this cqeriment,

a permanent mechanical scanning arrangement ms

chosen over an inherently puch more flexible electronic scanner because of the

better accuracy Kith which it could be controlled.

(iv) 13ux-q measurements hhateucr the cncrgy measurement being made, it ultimately depends upon measuring an ion current as a function of either the accelerating or electric sector voltages or both.

The magnet is often siciultaneously used to

separate the ion beam according to the momentum-to-chrtrge ratio of its con-

stituent

ions_

(3nly in a few case5 are mzxsurements under coilditions zip-

proaching high mass resoiution ever attemptedanalysis of the

product

Generally speaking, it is the

ion bean according to the translational energy-toFor this wrlr h-e

charge rzltio of the ions it contains that is attempted_

have soraetimes found that an energy resolution (301 valley definition) as high as 10,000 is desirable; in other cases energy resolution can be sacrificed in order to gain added signal-to-noise ratio_

The iqortance

of

si_gnal-to-noise ratio and the mtkocis of achieving high energy resolution

kave already been emphasized_ Kc

have been able to measure translational energy releases below 1 meV

[CtS],and for these narrow peaks and others to detect changes in energy release as 3 result of isotopic labeling [SS,SO), of varying ion source taaperature )sl,sr], of varying the accelerating wItage carrying out measurments

[53,54)_ or of

in different field-free regions [52,543.

These

changes have been used to relate the internal energy of the reactant ions tiitk frapntation

rate, to infer the presence of competing fragmentation

processes leading to the same product [SS] and to infer, for some small molecular ions that a tunneling mechanismwas responsible

pe& [Sl), Measure;nents of this kind have also ion enthalpies because they

for the observed

led tO improved

values of

allow corrections to 'be made for the excess

energy inherent in appearance potential measuwnts-

Ckw mu-k in this re-

gard has followzd

that of kanklin

actions

in which -&re

Several

recent papers have dealt

are

Kinetic

en-

of the imzchmirrrs of

reverse

Istry and therarochepl-

of all

fast

of organic

have also

topic

partitioning

only slightly

[60-62) _

in studies

(63-751 and in studies

using

negative

ions and partitioning

been i-epmtecI_ is tomrds

inteITOIw?rSiOns

can be obtained in excess of

studies,

ions 1791 ZUXIthe

reactions

Infomation

[52] _

from Estastable

the minimu

in the re-

occur

in tt8-orecent

in polyatonic

in uniraolccular

the cmplete

h*ich

is reflected

dissociations effects

upon re-

(SS,59),

of this

c?rtensiycly

ions

.Analogous studies

the energy

one on collision-induced about emxgy

been applied

This objective

ions-

second on tcqeraturc

energies

aspects

in which our work is akcd

characterization of

activation

energy rmz&ufCLMfnt (771 and bcith enere-

(XI)

The direction

but has concentrated

with various

fir;ignsntation

(66,74-76j_

cohcerned with kinetic

energies

large

measureiumts have also

on ion stiucture

actions

[19,56,57]

ions which have

required

for

frqmentation

can be campleszcntcri by the study of energy iSww - ‘This infomation partitioning accompanying collision-induced dissociations uhcre highly excitcrl

ions may be involved

energy loss emx-gy

uing

a-_

energy spectra

energy peak provides range of mcrgy

releascz

pncticc

this

suffers

of

loss

of

intensity

as a resexch

in their

kinetic

The position

loss;

frcma

of the kinetic

uickh provides

its

cscitcd

the

ions

rac;lsurc;m t5 ;rs shoun in kurk on

topic

of tcqcntu2-c

temperature of

(say

In

collision_

in diich

5%) on passing

suggested the km

through the target

pressures

gas_

are now being e.xplorcd

right, effects

the ion sow-cc

de~xmkncc

is strongly

detewincd

by tbo instrument usti effects

of a single

under conditions

at high target om

of the type just

be the result

on 13155spcctrmctric

in our uork from the observation

The obsermd

and the

the study of highly

frtxl proparRo1, show u~rkcrl ckpcmkxe

upon the

[Sl-S3]

ions,

cncx-gy

mcrgy

is achicvcxI by mrking

The subject

ion

both the kinetic

fra,Pracntation arc est kited

to thcmmcficarical analysis

occurring

If loss

tk

This brings

that the reaction

a small

the

the product

ion ki.lftic

&ktltipXc collisions

has arisen

of

_subsqwnt

studies

latter

[39]-

To he aaenabte is essential

its

a measure of

the comp3ss of

the lm-cr alcohols it

In thwc

accompanying excitation

release

the kinetic

within

[79].

[SZ]_

that certain of the Ben

fragmentations

reactions,

kinetic

notably

cncrgy release

more strikingly,

this

dcpcndent upon the time sczkle of the experiment ;Ls have ken

amI ion accelerating

tentatively

interpreted

voltage

~nployti-

as indicating

the

existence of w mechanisms of H' loss dependent upon different forms of activation of the ion and having stilar rates only in a certain narrow range of ion life times_ (v) peak shaps and distributions of kinetic energy relmse Detailed knowledge of the factors (instrumental and energetic) determining peak shapes has long been realized to be an important research objective [5,84-881, Improw?ments in peak shape can be brought about in several trays_ Trxo experimental devices have been fitted in the MIKE spectrometer to effect this. l%c first of these is an arrangement by which the lengths of the intermediate and final slits can be reduced. This causes an increased discrimination against product ions that receive 3 component of velocity in the z-direction (along tk..direction of the length of the slits) during fragmentation- Peaks are thus more dish-top@

and overlapping pea&

better

separated- The second device consists of a short enclosed region (of circular cross-section) located itzraediately behind the intermediate sift. hben a positive potential, S i'Olts,is applied to this reaction chamber, the ions in the main beam that have been initially accelerated through 3 voltaRe V are slow4 to a kinetic energy c(Y-X)_ if 3 fxqgmcntation reaction (1) El1*

*

al"

l

Q3

(1)

occurs within the chamber, the product m,l ions acquire a mean translational energy [m&V-S)]/y_ As these ions- enter the main field-free region in front of the electric sector they acquire extra energy es, so that their final energy is (m,eV)/ml + eS(ml-m-,/ml). On the other hand, ions that dissociate in the -in

field-free region produce product ions of mean trans-

lntioml energy m,/m,(cV) and the twr species of product ion can -be separated. The former ions have all been produced near the intermediate slit (a focal.point) and thus can be brought to a sharper focus- A sketch showing the new field free region is given in Fig_ S_ l'beratios of peak arcas depend upon the relative lengths of the the field-free regions- Consider a variation on this e_qxrtint using a very similar device, a short field-free region of rectangular cross-section in which the four sides are insulated from one another, the pair lying in the yz plane being at ground potential (this also being the potential of the front and back plates), the pair in the m-y plane having a potential between them- This can be used to deflect the ion beam and prevent it from leaving the region, lthenthis is done, only the neutral products from any fragmentationswithin the box will

c z

Ion bcom

t/”

Ecr --I -

12’

-

0_875-e

I

Sit 0_020m

)

I

r L

656-w

Scheaatic diagra of chamber fitted near the point of intemediFKlJRE 5, ate focus of the MIKE spectrometer_ Ihe potential within the chaaber is \&able so *at reactions occurring here can be distinguished fm those occwrGq elsewhere in the field free region, To ua.xi&te the fringe field gradientsandsoobtainahoraogeneous potential within the chauber it is 1ocatedbew3?ntw8gmunded plates ‘andseparated frm then by 0.033 inch. AX1 slits are O-220 inch long_ be tlansarittedand these can be ioniced subsequently by a bea of electrons or photons or by collisional e_xcitation_ Such a chaaber is currently under construction_ It shuuld also be noted that any such chaaber ~;i)', by fitting anzwro9f tube~hroughonewall,beusedas an evacuatedchadcr~-enthc main field free region contains collision gas or vice-versa, Recently it has proved possible to calculate the exact peak shape to be expected for particular energy releases, including in the calculation such factors as the exact position wit! the field-free region acre rcaction occurs, the diwergence of the hem and the dimensions of the slits [SS, S9]_ A ccquter prugryn has been written to enable distributions of energy release for any fmguentation to be deconvoluted frcnathe peak shapes and 'Jlisisaddingan

iqortante~rad-

mension to our understanding of the

energetics involved in the fram%tions [90]- -Already:several reactions have been investigated in detail and we are obtaining information concerning the shapes of repulsive potential energy surfaces (911 and such interesting infomtion as the length of the C-H* and C-D+ bonds iu the transition state

I23

involved in the release of H’ or D+ 1921. Some of the translational energy releases in the fragmentation of small doubly charged ions, for example those containing 2 or 3 atoms, can be as high as 10 eV 1931, These energies are effectively single valued and can be used to estimate the energy differences bemeen excited states. Even lapaer energy releases have been observed fm

small singly-char+

ions, One example is the fragmentation of

Hz+ Ehich can occur by collision [94]Through the analysis of peak shapes it has been found that the distribution of kinetic energy releases in a nuznberof reactions for which the average energy release is less than 100 meV is Doltzmann in form (60,90,95]_ Kc are currently

seeking reiationships betmen the mechanisms of fragment-

ation reactions and the shapes of the distributionsXlleability to c_saminemetastable peak sbapfs uader conditions of high energy resolution has led to the observation of structure in the peaks [55-37]. In particular, composite peaks due to the superpositionof Wo peaks arc observed Eith sane frequency [55,59,SO,96-loo], In addition to the trivia1 case of a coincidence in mass betxeen ions of different eltmental composition three situations which lead to different kinetic energy releases can be distinguished. First, isomeric ions may fragment by loss of the same neutral species. Second, a single ion my fragment competitively z&z t&o distinct activated complexes leading to tm distinct products. Third, a single ion ma)-fra_gmentV-5~2 a single activated complex but it may yield produc:s which differ for example in structure. in electronic states or in vibrational states. Examples of composite peaks due to independent reactions of isoaeric ions [9S] and due to competitive fragmentationsO&X different transition states [IOl] have been reported. The fomation of products in different states or havin, - ismeric structures via a single activated ccxzpIesis a less widely recognized possibility(vi) Ikperimeats -in which collision gas -is introduced Charge permutation can be brought about readily by passing a beam of ions of high translational energy through a collision gas_ The gas can be introduced into an entire field free region or into a specially constructed collision chamber [lOZ]- This latter method has the advantage that the ion/molecule reactions can be oadc to occur at the focal point of the energy analyscr, This leads to improved resolution as shorn in Fig, 6,

b)

i-_-L t

. 50

I

.

52

a

%ssFIGWE 6, Illustration of the resolution (and sensitivity) obtained (a) in a special collision chat&x and (h) in the &ole field free region for charge stripping reactions in which a singly-charged ion is further ionized- The tbreepeaks ineacbspectrumareduetomasses SO, Sand 52 inanilineCharge pemutation reactions are particularly sinple to study for tw reasons, Firstly, the kinetic energy acquired -bythe collision gas nolecules is negligible c-red with the change in kinetic energy of the ions [74,X]_ This latter energy can thus he equated directlg with the internal

eriergychangesocaming-

!ScomUy, b4iousc the electric sector lgeasures

kinetic energy-to-charge ratio, the sector voltage requir@ to transmit the productionscbanges by a large ammmtwhenthenumberofchargescamiedby the ions is altered. lltisrenders the products easy to separate from other (as incharge stripions- For exax@e, ifthenmberofchargesisdoubled ping of singly charged ions) the voltage for mansmission rhmugh the Forthis reason, mass spectraof electric sector is approxirmtely halve& charge-stripped ions are knoun as E/2 spectra [103]_ A portion of an E/t spectnrashovingcharge~~~ionsfromthehighpres~~;rassspec~ of toluene is show3 in Fig_ 7, The reactant ions are of misses 183 and 181

125

”

50

48

46 m/e

JJI 44

1 I

42

FIcaJRi~ 7_ Partial E/Z spectrm of ions in the high pressure spectrum of toluenc showing adjacent peaks in the normal mass spectrum used to establish the mass scale.

respectively [(2X-l)+ and (2M-3)+) corresponding to b/e values of 45,75

and 45.25

at normal settings of the mass spectrometer. Similarly, 215 spectxa [IO&106] are produced when the number of charges carried by the

ion is halved in the collision (as in charge exchange of doubly charged ions) and -E spectra

are produced Ehcn the sign of the charge carried by

the ion is reversed (as in charge inversion of positively 11071 or negatively-charged ions [lOS])_ These spectra c3n be used in tmLr8ays_ In the first, the B-slit of the instrument can be opened to its fullest extent to &llow all product ions of approximately the correct energy-tocharge ratio to pass, In this case, quite new kinds of mass spectra are produced and can be us&

in .analysis. They can also be used, just as are

126 nonml

charged

In this

good energy resolution_

the product

for

potentials

have been detcmined

actant

ion5 could be detected

States

in rhe singly-charged

be located

collision)

balruKcs

were studied

for several states

_

field

arks collision

froci one or

loss

[ 1101.

of the

of study involving

than the above spectm fomed

with

sugge~ internal

reacstions have been stuJi&

thm

iroleculcs

because energy

in all

reactant

of collision

d

gas

of

of ckrge

[92,112-X14),

perraut;ltion

is to the

of

ions by detemining

affected

iscareric

by the internal

enew

charge excknge

dissociation,


The nethod is valuable

[lTSl_

relative

relative

cross

because the results

secare

has been used to produce singly-charged analogs

ture of the product with that of singly-ch;irged inpact

can be used to

of the ions than is collision-induced

ions by kay of the doubly-charged

producnf by electron

Such

fra_pcnt_

qxcZr;l

coupare the structures reaction

is even broader

they might subscquent~y

in ~11 the 3bovc kifkis ions_

the

to the

C;ISM in which the product

of po2;itivc

organic

cxcitcd gas could

In the -IE qxctT;l,

cicctrons

study of the structure

less

re-

and energy gain

charge pemutation

interest in-0 appliczrtion

me paRicularly

for

(1091 Khile

[Ii1 I_

The px~~r;rl

tic+

ions

ioni-

of the singly-charged

to both energy

rho addition

double

organic

of

ion

In the cJsc of tE 5pectta,

could be studied

inwluing

energies

cnero,t ic info-t

ions of both reactant

of hrD ckctrons

x-emval

ions are

[X,55;

tal

from E/Z spectra,

excited

and peaks corrcsponciin~

(superelastic

the

case the exact kinetic

For e_xaaple,

the xa-e gas ions long lived

energy

ions arc exceptionally

ions can be ixeasuredandfundaaen

deduced from these values_ zation

that particular

The CnH6** and c H,*+ species arc c_xaoplcs of w?ry stable doubly n, -Alternatively, the &slit can be narroued so as to ions [I&l]_

stable, give

to infer

laass spectra,

and to vre

ions of the sa

The ccoparison

[116]_

abundances and shapes of the xwious

the strucforrwla

is nadc on the Isis metastable

of

peaks produced

fnxu both species. A variety fast

of other

moving ion and a collision

pertiattation, is detected

reactions

which utay be fcllowd

of the excitation

gas is present-

energy acquired

change of kinetic

be investigated

types are excitation

by fragmentation,

by the reduced arrxrnt of

way when the collision

consequent upon collision

gas molecule can also

lko such reaction

the sane equi-t_

its

types of

fragwntation

without

using charge

and deactivation, along a particular

_As previously

noted.

of energy release

which p3th-

the EKXUIvz~lue

by the ion can be measured directly

energy and the pattern

of 3

frcar

when the

127 oXcited ions fmSrnent can be determined from the shape of the peak due to arrival of daughter ions at the detector. A further insight into energy transfer processes and an extension of the range of applications of the mass >Tectroswer is afforded by the ability to study inelastic scattering_ Only preliminary experinents have so far been done, involving both the rare gases [117,llS] and a variety of organic canpounds [119]_ The I;I;FSS spectrxnzeterused (the INi-2) is far fran ideal for such ~surewnts, but this is an example of a field Ifhereit bus not been felt Hortbhile to build special cqu+rent in view of our interests lying nsainlyin other directions- Nevertheless, soraeinteresting results hwc already been ohtainod. The nethod used is to offset the ratio of the accelerating voltage to the electric sector voltage fro53that required to trait

ions centrally through the instrument so that

the

ion bean riill

not be transznittedthmugh and the energy spectrum

the &slit_ Collision gas is then introduced of ions deflected through the appropriate angle is

detcrrkxd, using the nragnctas a uumenturwto-charge analyzer ubile suceping the accelenting voltage over a snxrllrange. A further pssibility is to investigate ion-molecule collisions using ions sf low kinetic ener_gy_ There is already a large research effort concerned with ion c);clotronrososxxncespectroxze ters in which such collisions are inportant arkIit wsr &cided

that

it

kas

inappropriate to extend our

ohn research in this direction_ However, the acquisition of a high pressure source capable of operating at up to 1 torr pressure has led to the conclusion thar SOBC sighting e_xperimentsto assess the usefulness of the source for smthesising dineric and similar ions mmld be wx-thuhile. Fig. S shows an exor@e of the kind of infomation obtainable_ The MXE spectrum using collision gas for the ion at rrrass-to-charge ratio156 inbenzene shows the fm~~ntation infomtion

paths of this ion in sufficient detail that structural

about it can be obtained in just the sac IQ>?as structural

inferences are dmhn concerning fra~guenting ~lecular ions under loo pressure conditions- The source has other applications r\henused as ;ichazical ionization source and thcsc are discussed in a later Section(vii) Experixaentsinvolving ion/surface reactions The subject of Zen/surface reactions began, as far as our research ws concerned, with the chance discovery that as the ion beanrtranversed a narrow tube that kas being used to improve the differential p-ins betwwnr Wo regions of the RW-2, chzge inversion was occurring_ Energy-measureraentsshowedthatthrrelectrons

hxxegained

by theions~-ithanexpenditure

128

___Al JLd-

Oh

FIaRE

0-k

s_

pressuresounce-

Thesp3Axumx3.srecorded

using

fozxed in a high ter

usirrghydrogenascollisiongas-

of mly

a total of same 10 eV of energy and pointed to their origin from a

metal surface. The collision, at glancing incidence, betmen beam and in the=-direction. Otherreactions surface occursduetobeamspreading induced byametal

surfacewerefomdandtheirenergeticsinvestigated. It was found that all the processes previously studied using collision gases could be observed [X20], Later, it was demonstrated [121j that dissociatkms follouing ion collisions with the -11s of the flight tubeh7ithinthe magneticsectorwerethecause

oftheanonulousmetastable

peaksthathave

129

remained uncxplaimd

for a number of years

mys more convenient

for collision e_xperiments than is a gas, and ion/sur-

face e_xperiments may find application

[122,123] _

A surface

in the investigation

is

in many

of inelastic

processes and in surface analysis-

Some new methods with applications to chemical analysis such as ion/surface i-eferred

interactions

and 2E and related

Hcrc we discuss,

to-

energy spcctrouotr?;

mass spectra

in particular,

have already

the potential

been

of ion kinetic

in molecular structure elucidation_

For the prime user, the organic or biochemist, mass spectra are diffilhcre

cult to interpret_ structural by long

is too nuch information

significance.

In particular,

alleviate the problw

many of the lor\er mass ions,

For some t&e in structuml

the deveiopnent

elucidation through more convenient

energ)- scan_ (i)

integrity

(ii)

in a

Currently he are involved in an attempt to sizxpiif?; the molecule

Ideally one seeks to satisfy

should he ionized

the fra_mtation

reactions,

reaction products, should be characterized knom

spectrometer rrhich

of a chosen ion to be follomd

further the structural elucidation problem these criteria:

Nest significant, in this

of the reversed sector ME

conueuicntlp allo~c~ all the reactions

tural

formed

we have sought, with many others, to

netbods of recording motas~able ion transitions.

sin$e

or no

of succcssivc fragmentations, are of marginal value in

squcncc~

structural elucidation_

regard, KS

which is of little

collision

rather

loss

of struc-

than merely the

(iii) reactions should be of

type and preferably simple bondcleavages_

in large part by studying

without

These desiderata are met

induced dissociations

in the irlIKE sptx-

trumeter using a method of ionization other than electron impact such as chemical ionization or field ionization. ions or qu3si-mlccular pro&~~ed

These techniques give aiol+xlar

ions th3t have lower intern21

energies

than ions

by other methods and thus, ions that are less likely to iscmerize.

Roth methads do, however,

produce the ions under conditions of high local

pressure so that subsequent acceleration of the ion beam may excite the -By studying

ions-

collision-induced

dissociations,

arc closely satisfied, the latter criterion better frqwntat

ions are observed _

tion of the &HE

An illustration

for chemical

meter-

(ii)

of the value

and (iii)

metastable

ion

of the combina-

spectrometer and collision induced dissociation appears in

Fig_ 9 that refers to a substituted pyridine, able

criteria than Ben

ionization

A high pressure source

suit-

hxn-k is now being added on the MIKE spectro-

130

78

92

106

43

p9 0

20

%

40 ESA (x 104

(b 1 flqn Pressure

~00,

60 y

(It IO21

.i_J 80 -y (x ro4,

100 - (Xl)

106

80_ <-

152 .

I79

60_

zZB 40,

43

2 0

78 0

20

92

40

,“S . 60

.

. 80

152 .

100

Yo ESA FICZIRE9, EXIKIZ speclxa of the molecular ion (m/c 179) of 3-(2-pyricIy)-l)propyl acetate takeu in the absence and presenFc-of a collision gas. The three peaks seen only when collision gas is added a11 correspond to collision-induceddissociations and are particularly useful in deducing the molecularstnxture_

The use of isotopically Iabekd species has many obvious applications in analysis and the methods described in this paper offer some extra advantages. Measurement ofmetastable peaks has advantages in dctcming the extent of isotope incorporation [l%j, but another study perhaps illustrates more viwidly the power of the new methods,

It has proved possible to study

isotopic species at natural abundance and to select a metastablc peak due to a particular fragmentation of a specifically labeled species without prior separation of this species from the mixture of labeled and unlabeled species present [SO], Stereoisomers have also been distinguished on the basis of the relative contributions of two processes in a composite metastable peak [US]_

Inthisarticlewehavechosentostresstheins

tnnaentatiouandthe

effect it has had on the direction of the research, interesting obsermtions having suggested the modification of the equipment to develop further new

branchesofenquiry. A willingnessto mxlify instrumentation, not willynjillybut efficiently and

single-mind&y

vzith

a

particular objeive

in

view, must be regardedas an importantpart of experizientalmass spectrometry: Looking at merging trends in ion kinetic energy ~pectrometry in tems of contributing instrumental develomts we are seeing or hope to see a further significant improvemeat in energy resolution occasioned by hi0 developitems (i) the extra sQ?+nal-to-noise ratio available by the use of imaging detectors and (ii) the use of small field free regions at particular potentialsandpressures as reactionchambers, these regions serve to define more closely the position of fragmentation and the direction of motion of the products_ With these developments structure in metastable peaks for poly-atomic ions may become a routine observation, Aaother area ripe for development concerns ion production facilities_ ll~ecozrthined requirement of more intense ion beam with energy homogenei~ and suitability for organic compounds has received too little attention in the years since Nier satisfactorily zmsmxed the needs of an earlier day. Ke are now exploring planoatron ion sources in this connection: the situation in \\fiich the most ccmmonly en#oyed ion source ionizes only about O-015 of the sample calls, in our opinion, for a large and broad-ranging research effortWiti the further improvementin signal averaging anddataprocessing devices the possibility of the routine study of successive processes in Studies ofthis typedone different regions of the instrumm topensupso far [92,116] have been of great interest since new ionic species can be prepared using high velocity ions with the attendant Fssibility of their characterization. There appear to be so many obvious extensions to the instrumentation

structural and thermochMca1

and techuiques and such a wide range of subje

(covered in part in recent

reviews [26,32,126-1291)in which new and exciting measurements can be made that the stage is surely set for a continuing growth of the subject of mass spectmmetry, especially in those aspects involving the various facets of ion kinetic energy measurement.

Kc thank the ~XationalSciemze Foundation for their continued financial The hark of se&-en1 ccw2nbex-s of the EUSS spectx-cmet~ of this hXWk.

sqport

the instz-went group is gmtefully xbiowledgeci_ rcsem-chgmupandof Without their efforts none of the hark done at Purdue h-ould kn-c been possible_

l_ R_ F- Ki,?kzog, Int- J- Zbss Spcctrom- 4 Ion Phys-, 6(197I) _Xo.5/6_ 2, A. 0. f. Xitr, Int- J_ L\hssSpcctroix G Ton Phxs,, S(1972; .Xo,4, 3_ J_ Natmuch, 3, :Xaturforsch_.lOa(1955) .xu_II_ 4_ F_ H_ Field d 3. L- Franklin, "Electron Impact Phenomena d

the

Properties of Gaseous Ions" Asademic Press, (195i)SZ_ 5. J- H. Beynon, R. d, !%tdcrs and A_ E_ Williams, P_ ~Xaturforsch-, Xb(1965)1SO6. C_ Ottinger, Phys, Lett,, 17(1965)269_ 7. N. EQrber, h',R_ Jennings and R, Rhod,~ 2, _%turforsch-, 2&(1967)15_ 8. F_ K- k&fcbffertyand T- &I_Shannon, J. _&xcr-Chum- Sot-, SS(1966)50119. A- S_ Newton and A- F_ Sciamama, J_ Chem

Phys., 50(1969)qS6S.

10. I;_L. i\bhler,V_ zi_Dibeler and R_ MI,Reese, J_ Chem- Phys-_.21(X954) 394. 11. J- Olmsted, Ii-Street and A, S. Newton, J_ Chm_ Phq_, 30(1964)2114_ 12_ C- 2. Berry, Phys:Rev_, 7S(1950)597_ 13. &I-C- 1nghz-m rud H- E- Stanton, J- Chem. Phys., zS(195S)9_ 14. R- Tmbe_rt, T_ rtiturforsch-,19a(1964)91115. C- C- Rodand. J- N- D- Eland and C_ J_ Danby, Int, J_ &bss Spcctrom Ion Phys., t(1969)45T. Int, J_ .&hssSpectrum, Ion Phys-. 7(1971)79_ 16. C_ C_ Rm&md, zutdJ_ L_ Franklin, Int_ J. &SassSpectro~ Ion Phys-, If- DI K_ Sen SJmw 13[13i4)1391s. J- L- FnrJtlin, P- PI_Hierl and D- A_ Khan, J_ Chem. Phys., 17(1967)319S. Franklin, J_ Chem. Phys-, 48(1968)409319. $1.A. Haney and J_ f.., 20. Ly_R- IMy, Prm- Phys- Sot- (London), 85(1965)897. 21, For earlier measurewnts employing retardation see reference Ii and r&s- 2-6 therein22. N- R- Daly, A- WComick,

R_ E_ poh-elland R- k+x?s. lnt- J- Mass

Spectrum- lon Phys-. 11(1973)255_ 23. S- E. Kupriyancw and A_ A_ Perov, RussJ- ph?rs-Chem-, 39(1965)S71-

133 24.

J. Ixlrup,P. Foumier and P. Dong, Int. J. Bhss Spectrum. Ion Phys., Z(1969)311_

25.

J. LAW, Ber. Wmsen-Gesellschaft physik. C&m.,

26.

R. C. Cooks and J. H. Beynon, *'IonKinetic 3ergy Spectn>metry'win A. C~CCO~~ (ed.) Mass

?7(1973)640.

Spectronetry, InternationalReview of Science,

Physical Cheznistry,Series

Th’o,

in press.

27.

J. H. W_ynon, J. #. _Wy and #. E. Baitinger, Chem. Coznnun.,723(1969). 25. J_ H. Beynon, J. I$.i\in,v and T. mtsu, Int. J. Mass Spectrom. Ion Phys., 3(1969)47. 29.

R. IS.Kiscr, R_ E_ Sullivan and M. S. Lapin, _&al. them., 4l(1969)1955.

30.

F. ir'. rWl;rfferty,J. O-to,

31.

Ir'. t\bjor,Org. Mass Spectraa., 2(1969)751. A. H. Struck and H. W, Major, paper presented at the 17th Annual

H. Tsuym,

Y. Xakajima, T. %da

and H.

Conference on Mass Spectranetry and Allied Topics,-Dallas, Texas, 1969. 32.

R. C_ Cooks and J. ii.Beynon, J. Chem. Ed., 51(1974)437_

33.

R_ C. Cooks and B. H. Solka, paper presented at 23-d _AnnualConference on L&hssSpectraaetry and Allied Topics, Houston, Texas, 1975.

3.

R. D_ Craig, B. X_ Green and J. D. MIdron, Chimia., 17(1963)33-

35.

T. R, Govers and J. Sc@nuan, Cher;r. Phys. Lett., 12(1971)414.

36. P. C_ Foumier, T, R. Govers, C. A. Van de Runstraat, J. Schopnx%nand J. Los, J. Physique, 33(1972)755. 37. R. C_ Cooks and J. H. Beynon, Che% Co=nun.. 1352(19X). 36.

3. H. Bc]xwz, R. G. Cooks, J. W. F&y, W. E. Baitinger and T. Y. Ridley, Anal. ChaJ., 45(1973)1023.

39. J. H. Beynon, T. Ast, T. Keough and R. G. Cooks, Int. J. Bbss Spectracl. Ion Phys., 16(1975)343. G_ R_ Lester, 'Wetastable 40. R. C_ Cooks, J. II.Beynon. R. $I_aprioli artc! Ions'*,lflsevicrPublishing Co., (19733 chapter 3. 41. UnpubIishcd data, GELAl Ltd, &Is50 mass spectroraeter. (in press). 42. M. J. lacey and C_ C. Mxdonald. Chen. Cm.. 53. A_ F_ Weston, K. R, Jennings, R. W. Elliotand S. Evans, Org.

NSS

Spectrael-.(in press)44. D. L. Kenp, R. G. Cooks and J. H. Beynon (in preparation). 45. J. H. Ge_ynon,D. 0. Jones and R. G. Cooks, Anal. Chem., (in press) 46. C_ E. Giffin, H. G. Eoettger and D. D. :Xorris,Int. J. Nass Spectrom. Ion Phys-. ~5(1974)43747. D. T. Ten-zilliger,J. H. Beynon and R. G. Cooks, Int. J. Mass Spectrotn. Ion Phys-, 14(1974)15.

134 46,

R_ C, Cooks, h- C- Rim and J_ H_ Beynon, Chem_ Phys. Lett_, 26(19&I) 131.

39_ J, H_ Beynon R. M. Caprioli and T_ Ast, Org. i\hssS~ectma., 5(19X) 229. 50. J_ ii_kknon, 11,F. Brothers and R_ C, Cooks, And.

C&m_, 46(1974)

laY_ 51. B_ H_ Solka, J_ H_ Beynon and R_ C_ Cooks, J_ Ph?-s_Chcm., (in press). 52, &I_Naked, R, G_ Cooks and J_ H_ Beynon (in prcpmzation!. Spectraax. 53, J. H_ Beynoa. J_ A_ Hopkinson and C. R. Lester, Int. J. n\l;lss Ion Phys-, l(l%B)3554, R_ C_ Cooks, K_ C_ Kim, T_ Keough and J. 11,Beynon, Int. J. %hss spect==- Ion Phys,, l5(1974)Z71. 55, J_ kt_Be>mon, Ml_Bertrand Yut R_ C_ Cooks. 95(1973)1?39_ _

J,

.&ax_ Chaa. Sas.,

56, P_ bXataIisand J. L. Franklin, J. Chem. Phys., 69(1965)294X 57. D_ K_ Sen Shanea and .I_L_ Franklin, J, Amer, Chem SB. E_ C_ Jones, J_ H_ Beynon and R, G. Cooks, J. Chm,

Sot_, 95(Wi3)6561. Phys., 57(19X!)

2652, 59. R_ G_ Cooks, K_ C. Kim ad Ph>T-. 15(1974)Z45_

J_ H_ Beynon, Int. J_ I&lass _+cctram. Xon

60s J_ F_ Elder, Jr., J, H. Bqynon and R. C. @c&s, Org. bhss Spectrum., (in presr), 61- F_ P_ Loss@, 62, J- L- iMazs

C&ad. J, Cberc_.50(19?2)3973_ and C- N- bbeese,Org- Mass Spearan., 9(1974)616.

63. .I-H. Beynon, R, W, Captioli, R, G, Cooks, X, &I_M. sibbering and T_ A. Molermar-Iangeveld,Org_ ,NassSpectran., (in press). 64, T_ Keough, R_ H. Shapiro, J_'._l_ Beynon anciR, C_ Cooks, 2. zXaturfor?;ch., x -.; 29a(l97~)507_ 65, J-H_ Beynon, &I.Bermmdd

R_ G_ Cooks,Org_ amassSpectrau.,

7(1973)785_ 66. J. H. Beymm and T, Ast, Org, Mass Spectrom., 7(1973)50X 67, J- H_ Beynm. R. M, Caprioli and R. G_ Cooks. Org. 3-s

!$xxtrom.,

9(1974)1_ 6S_ .I_H_ Beynon, R_ M. C?prioli, U. E_ Baitinger and R'.0, Per=, J. Mer. che!n.Soc.. 94(1972)6528_ 69, 3, H_ Beynon, R_ II-Shapiro, K_ Tamer and R, N. Caprioli, Org. Zhss spect==. 3(1970)1593. 70, J- H- Beynon, R- N. Caprioli, R. H. Shapiro, K. B_ Taaer and C. U_ J_ Cbang, Org_kass Spectmm-, 6(1973)S63-

135 71. J- H_ Beynon, W_ 0, Perry, K_ E_ Baitinger, J_ 1~.Amy, R_ M_ Caprioli, R- N!,Rexmud, L_ C. Leitch and S. Meyerson, J. Amer, C&m_ 92(1970)7236,

Sot.,

72 J_ H_ Beynon, C_ Eadon, C_ Djerassi and R_ M_ Caprioli, Org_ Mass Spectran., 5(1971]917_ 73, J_ H_ Beynon, R_ El.Caprioli, R_ Ii,Shapiro and h. B_ Tamer, Org, Mass spectl-ca, 3(1970)1333_ 74_ R_ G_ Cooks, J_ H_ Beynon and T_ Ast, J. _Amzr_Chem, Soc,, 94(1972)1004 is_ T_ _Ast,J_ H_ Beynon and R_ G. Cooks, J_ _Amer.Chem. !3oc.,94(19X)6611 76, R_ G_ Gmks, T_ Ast 2nd J- H_ Beynon, Int, J- Mass SPectram. Ion Phys,, 16(1975)38_ 77. J. H. Bohiieand S. G. Hart, Int. J. Nass Spectma. Ion Phys., 1X1974) 319, 78. P. K_ Harland, J_ La Franklin and D. E_ Carter, J. Chem_ Phys., 58(1973)1330_ 79_ R_ G_ Cook.

I,_Hendricks and J_ Ii.Beynon, Org, Mass Spectrom., (in

press). SO, IX_C_ Kin, J_ H_ Beynon and R_ C_ Cooks, J_ Chem

Phys., 61(1974)1305.

Sl_ W_ WGOIX~~ and L_ Ker~ia, Canad_ J_ Chem_. 41(1962)316_ 62, F_ &I_Rourkc, J_ C- Sheffield, pi.D- Lewis and F_ A_ \tXite,J_ Chem. Phys., 31(1959)193. S3_ J_ H_ BekTon, &I_Bertrand, E_ G_ Jones, and R_ G_ Cooks, Chem (19i2)311_ &I_ BI_C_ Flowers, Chesn.Camam,,

Ccmmn,,

(1965)2X.

85, J, H. Beynon and A. E. Fontaine, Z. hbturforsch,, 223(1967)334_ 86, Ii-C, Smyth and T, K, Sharmon, J. Chess.Phys., 51(1969)4633_ 87, V. It‘_ ,Naslen,Int. J. Mass Spectrom. Ion Phys., 13(1974)207. ss_ J_ H_ Beynon, A_ E_ kmtaine and C_ R_ Lester, Int, J_ Mass Spectrom Ion Phys., 8(1972)541. 89. D_ T_ Terwilliger, J. H. Beynor~and R. G. Cooks, Proc. Roy. Sot. (imdon),‘31(1974)155, 90, D_ T_ Terwilliger, J- F_ Elder, J_ H. Beynon arrdR_ G_ Cooks, Int. J_ bhss Spectrom Ion Phys-, 16(1975)225. 91, R_ G_ Cooks, D_ T_ Terwilliger and J- H- Beynon, J_ Chen_ Phys,, 61(19irt)1208_ 92, T, _Ast,Ph_D_ Thesis, Purdue Universiiq-,1972, 93. J_ H. Beynm, R. 81.Caprioli and J. K. Richardson, J. Amer. Chem. -3x., 93(19?1)1852.

136 94, J- H- Beynon, R_ Mm Cooks and R. 81.Caprioli, &oc_

Roy_ !%c_ (London),

327[1972)1. and R, 6, Cooks, (in preparation)_ 3(1970)SS_ 96, K_ R- Jennings, Ox-g-rMassspectmm,) 4j196s)125_ 97, J_ H. Beynon, Mvances in xass spectroc5etry, 9s_ J_ L_ Holmes, D_ ~NcGillivrayand Xv,S_ kaacs, Org_ Nazx Spectrum, 9(1974)510_ 99, R_ C_ G3oks, %I_Ikrtmnd, J_ ti,Eeynon, &I_E_ Rennekanp and D, 15, 95, J_ F_ Elder, .J.II.Beymn

Setser, J_ her_

Chem soC_, 95(1973)1732_

Beynon, N, Bertrand and &I_K. Hoffman, fig_ Mass MJO- R- G- Cooks, J_ tE'spect=-. ?(1973)1303lOl- R_ G_ C&&s, D, If-Setser, f_ R_ Jennings and S_ Jones. Int_ J, Mass Spectraa, Ion Phys_, 7(1971)493_ 102, J- II-Beynon, R_ G, Cooks and T_ Keotrgh,Int, J_ Mass !$ectrcm_ Ion 13(1974)457_ I%=, 10% Ref, 40, pp_ 135-140, .A@-,orU,_%~?rs IOJ- J_ H_ Be,yrmn,R, &I_tiprioli, N, E- IkiitingeramI J_ Dr‘, s(lno)455. Spectm-, 10% T_ &t, J_ Ii_Beynon and R_ C_ f&oks, Org- &ass Spectroa, 6(1972)X9_ 106, .I.II.Beynm, A_ hkathiasancIA_ E. #illiams, Org- L-S Spt?ctrxm_. 5(1971)303_ 107. T_ bough, J_ If_Ekynon and R_ C, Cooks, J_ _iaer,Ckm. 1695.

Sac,, 951(1973)

10s. .I.H_ Emit, paper presental at the 3rd Australicrand ;Xeu2c~l;tnd&ss Spcctramctry Gonference, Canberrz, Januaq-, 1975, lO9- T_ Ast, J_ H_ Be>nrm and R, G_ Cooks, Int- J, .%ss Spectn?z~_Ion Phys_, 11(197i3)390_ llO- T_ _&t, D_ T, Terwil?iger,

J_ H, Ik~mon and R_ C, Cookq _I_Chcm.

Phys-, (in press). lll- T_ Y_ bough, J_ fi_Beymn and R- C, Cooks, Int. J_ &ss

,Spectroa.ton

pfiys-.16(1975)417. 112- J. H- Beymon, R, N. Caprioli, Ps.E. Baitinger and J_ U_ &my* Org- Mass 3(1970)455. sp"f=.. 11% D, L_ I&%& R_ C_ Gmks and J_ H_ Beynon [in preparation)114. T_ IV-Keough, J, Ii.Beynon and R_ C_ Cooks, paper presented at 22nd Amual Conference on Mass spctrometry and Allied Topics, Philakfphia, Penn,, 1974, 115- R. C_ cooks, J_ H_ Be_ynonand J_ F_ Litton, Org- Mass Spectrom-, (in P==)-

137

116, T_.Keough,T_ _Ast, J. H. Beynon and R, G_ Cooks, Org, kss

Spectrom.,

7(19x5)245. 117. R. C. Cooks, K. C. liim and J. H. Beynon, Chem. Phys, Lett., 23(1973) 190. 118. T_ -St, D_ T. Terwilliger, R_ G. Cooks and J. H. Beynon, J. Phys. Ghan., c 3n p=S)119. M_ LWdved,

R_ C_ Cooks and 3. H_ Ekynon (in preparation).

120. R. G. Cooks, D. T. Ikerwilliger, T. Ast, J. H. Beynun and T. Keough, J. .4mer. Chem. 5oc., 97(1975)1533. 121. R. G. Cooks, T. Ast and J_ H. Beywn,

Int, J. iMass Spectrcxn. IOQ Phys.,

16(1975)315_ 123, J_ H_ Beynon, A. E_ Fontaine and C. R, Lester, Chezn. Gnmzun., (1965) 265. 123. C. Lifshitz:, M. Shapiro and R. Stemberg,

Israel J. then., 7(1969)391.

123. J. H. Be>mon, J. Corn, Ir'.E. Baitinger, J. K. _ky a& Org. Mass Spectraa.

R. A. Benkeser,

3(1970)191,

125. K. C. Kim and R. G. Cooks, J. Org. Chem., 30(19?5)511. 126. J_ ti, Be)mon and R. 31. Caprioli, "Biochemical Applications of Mass SpXWOX&I?'",

J. Wiley and Sons (G. R. lfaller, ed.) (1972).

127. J_ 11. Be_ynon and R. C. Cooks. Research and Developlment, 22(19X)26. 125. J, H_ Beymn,

R. $1. Caprioli, k'. E. Baitinger and J. W. Amy, &&axes

in Mass SpecZrcxa., 5(19X)297. 129. J. H. Beynon and R, C, Cooks, J, Phys. E_, 7(197;1)10.