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A spectrum stripping method for the computer-coupled activation analysis of unknown samples by γ-ray spectrometry
AwoJylica Chimico Acla
Publishing Company. in The Ncthcrlmds
Elsevlcr
Printed
349
Amsterdam
A SPEC’I-I
Rapid 1)s
y-K14
ill-c
ilVililill)lc.
Siklll])lC
instrunwntal
of
Of tllc
:llltl
part,
tllc
Of
of
results
cast
of
IX!CilUSC nature
witli
il
i\ y-ray
isotopes.
Several these
of
met.
at
CC cd.”
and
metlids
spcctruin tlie
a ~1liljOI’ with
coniph
It Wit11
IElst
few
i1
)IilVC
of
discussed
sonic
procedures
.‘-I”
hen
VillllCS,
of
tllat
spcc’tra IC’.’
if
Will
.’ in
tlIC
f down
un.wsIm ted
or the
of
nown
ON
UIlCO’l
ICVCIS
tllc
f’.
cutc’e-
stlcavn
of tlic y-r;,)’
Alifts
)I
Irltd
Of
I1 iti(:lli~
rc\*icwctl
lXC~:lltly
‘I’lic
of the
OfI
llot
Vi1ryillg
counting.
least-squares
lens
sarllplcs
is
Colll-
the
*iin
lnfi
I tl
n-
Icrns
.tt1
1). proi
&:. .a
and
preSt!nt
nxdlod,
tlie
pllotopenk
library
which
is
is pedd likely wllich
l>itSC
provisions could
witli
IInvc
viiryirlg
conditions
gain
d;lti1
illt~lOU6~1 several
but
been
use<1
tlcgrecs
in
tllc
SUCCCSS.
of
il
IlC
I
0:
,L. Nay ideal stripping have 1’ AKIJERS ,\sI) BI:A>IEI<~ Ilnvc rcportcd tlmt a “slli~clow pe;tk stringent
consiclerablc spectrum
saniplc
etc.
SpXtril
instance.
For
WllC!n
incorporates
stripping
Iaowcvcr,
is recorded
ground
ilIlt
inulticoniponcnt
cases,
rC?SUltS
tlic
S;;llllplCs
of of
tiic
ilS
from cacll
howcvcr,
prescncc
number
spwtronietry.
of
EMI~I<\-
tile
large
of
clioscn illltl
tlic
ilCtUZ\l
inetliod,
arId
wcigilt
rlletllocls.
;inalysis
of
nutnbcr
least-scluares
tllesc
y-ray
spcctronictcr
unsuspcctccl linear
Iilrgc
a
tllc
ilClliCVC.
2. It
aiial~liis tllc
y-ray
colnp~nc~~ts
clclllctlts
to
usccl’o
witll
tllc of
authors,
often
activntecl
iiiulticoliiponcnt of
cooling
difficult
ICilSt-SqU;lWS
shifts,
when
by
niorc
tllc
t Ire
Si111I)>lCS tccliniqucs
;Lfl unknown
contrilmtions
rlIiltly
ICilSt-S(lUilN?S
ant1 hSc-Iin42
il~lillyZCt1
WllC?Il
occur
tlw
niorc by
is
‘IIIC
ones
activation, spcctrul
COlll]X~lXblC
quite
mi.sturcs.
cxpcctcd
arc
Villi
arc
gain
Of
which
of
for
is tile
in
dctcrll~ini~tiorl
\vciglits
unknown
reduction
S}XXtril
ttie
SugKcStcd
cm2
arc
synthetic
of
Spcutrunl,
rnCtllodS tllc
wllicll
i~l>sc~~ccof
Ixen
niisetl is
tllc
of
(lilta of
lil)rxy
; (2)
iIViLililblC!1~‘5
sclcctcti
Wliilbk
illl;llySiS tlW
using
IitrgC! nuinbcr
;I
if
C0llCcIltriLti0ll
using
mmsurenwnt
Sc\*crill
assumptions
yield
cornlmtcr
IXlrilllll!tCrS
tcchiiiquc
ccrtai11
(f)
SillI~~)l~
tllC
tile
tllc
tllc
clerncntal
SiLIll~~IL’
IllctllOtlS
Ollly
tllC
IXlrtS:
Of
ZlllillySiS
pKlCtiCil1
Of
tW0
Ili1nlcly
cx~tll~xm21lts fitting
IX
ilCti\‘ilt~
one Of tllc scvcr;il ClClllClltS Iwcscnt in 1mrators
CillI
hI~ilSU~clll~llt
consists
spxtruni
first
;lctiviLtion
S~XXtr~~lIlCt~~
yield
f
off
sllifts. to
fIYJll1
\JC ZLffCCteCl
ilfC
ncitlicr
on
tllc
“pxling
to
correct
txttcr
a COlIIpkS
Equally
for
true
is
by
l&r&!
smootllcd tCC~llliC~UC”
gain
shifts,
SpeCtrUln
the
fact
if
tllat
StatiStiCal nor
weiglitcd
llscd
by
counting
tk
SpCtrUttl
unscrambling scatter
in
properly. previous statistics,
tllc ‘I’llC
aUtllorS, back-
results.
R71uf.
Cltinr.
Ada.
38 (1967)
349-356
.S/~ectr~m
~rocctfrrrc.s
sCri/)pirrg
‘!‘!lC
f~!!(J\Vill~
I~lulticoin!~oncnt (f) nuclitlcs
For
any
(!il,rrlry
t;ikcn
for
iwing svstctn
IllCilSUrl!
tlic
counting
s;iIiic
Icrigtll
of
xctivatctl
s>‘stcin.
tilllc
arc
of
l)ure
OlItilitl
tlicsc
iis
tlic
computer
analysis
c,f tlic
s;iIiI!)!c.
f~f il nunilwr
slwctra
of r;lt!hJ-
!)ilCkg:r~JUIll! ~!lOu!t!
.Xiltur;l!
intcrcst.
;l!So IN:
cx~ulltccl. (witli known wcigllts) of tlw clcmcnts time ant! c~orintC~~1in tllit s;ime counting slwc:trurii (JI tllc sxnii: !c*rigt!l of time i<
riltli0lIUc:!i
:~ntl tlic stancl;irtls for a known A n;itiir;\! I,;ic-k~rcJun(l
;lc.ti\*:ltcc!
/II,,..
for
wn!~!c~ycd
tlic
wliic*!~ arc
s!)cctr;l)
for any (.j)
13acli
of
tlic
S!Wl:tril,
inc*!u
tlio
fitting ii tliirtl or
l)y
rnctl1oc!
(4) Ixiscd
It’,, tllc
~ivcn
arc of
wcrc:
t;lkcIl.
sInoot!ictl tlic
s!JcctruIl~
‘I’IIC s;~lnp!cs
(2)
a~lsc,
!“““!
y-ray
rclittiOT1
II,’ , = 1 +
I/I
Ii;itur;l!
Ixlc~k~:rc~lliIc!
t!lrOug!l
;l writs
wc:i~!itct!
of
usinK
s!Jcx:trilI1l, 5 (IZltil
;i
is
!xJints
wc4gliiinC:
for i!~t~*!Ic:ll~ltlllc:! l’ollllt,
il5
tlicll using
factor, Kivcn
(f~,/C,)I<)lJ~~
I)!
(I)
tllc c3)llIlts in clw~nc!! i ilnt! nl= I’(.*I. ‘I’tw rcslwc.tivc naturrl! Ixlc:k~rount! is tllcn suld rxtctl frcltn O~C!I t jf tlw ;lllOVC Sicilll!
(,‘I
is
(5)
~~TY~pXlll
ci3cr;‘wtl
:‘S
Iiltcr.
I~rotn
tlic
sliiftctl
st;lIit!;trc!
S!wctrutn
Cl/C,,
ratios
;lrl:
counts in tlw it!1 cllmnc! ant1 (.‘,, is tllilt in tllc !w;tk cl~annc!. l;roln tlicse ratios , 11~1tlw counts in tlw rcslwc.tivc !wak c!l;mncl of tllc sampIt! slxxtrum, :I )‘-rily slw. t111m of tllat coil1!~oIlcnt is p!ncratrrc! ant! tllcn sul)tractc!t! from t!lC! conilxAtc slx:trtir~i. ‘!‘!iis gcllcrilti(JlI illlt! sucwssiw sul,tr;iction of tlllt spectra is c~wtinucd until 111~~ ~llilr;lc.tlrI~i?;tic: s!wc*tI*liti~ of tlil* c!cnsirc*c!clcllicnt is ~wc~lot! off.
rwasurcd.
\~!~cIv f I I:. tllc
‘I’IIC scalctl
U!)
grount!
as
y-WY !ly
slwtrutll
IllU!ti!>!ic~iltioIi
clcscrilml
allow.
01 tllc wit11 If.
!Jy
i\ctiViltl_!t! tllc
St;lll~!ilIX!
\vcigl:lltiIig
viSu:l!
Of
factor
till2
atid
~!SillnilliltiOll,
~ll2Ill~:llt
is
ccxmx*tc
for
il11 iln!)urit>p,
SlllOlJtllC!ll, tlic
Ixlck-
front
citlwr
sainplc clmtilillcr or
tlW
of
following xl
tllc
rcs!xxtivc
!~~lSt-SC~U~lWS
(k-lk -fl,‘
stanclard, fl~rllllllil
iI:ilIiil~izinc: for
il siiiK!c
tlw
cliffcrcnrc
~0lll!~Oll~tlt
htwccn
its
of !mrc
tile two 11)
:
.fllc) .v’lk = c)
~vhC!rC \‘lk rcpx!nts t!K! umnts in t!il! it!1 c!limtlc! clement /2 in tlic saniplc xnt! pr is tlic! !woportion
tllc: \VilS
(2) Of
t!lc
Shirdard,
.rlk
t!lOSe
of tlw St~tltli~rtl spectrum
dw
t0
of tlic
elenwnt k in tlw sample. From this prop0rtion, stantlnrd wxl the pr\r,?mctcrs usecl for activation elcnicnt in the sarnplc is computed.
tlic weight of tlic clctnent nncl counting, tlic weight
in tlic of the
‘J’lw complete computer progrrrtn usictl for the ilCtiVi\tiOn nndysis of tllC unknown SilltlI)le by tlw spectrum stripping mctlwtl is dcscrilxxl clsewlwrel~. The main pr0gr;lfll, coded in Fortrzm I\’ for nn IB!U 709_1 computer. consists of a group of sulxoutincs wliicli ni:ly lx c;tllcd in tlrc Jx0Jxr scqucncc to Jwrform the ViLlh.ls oJ)criltionS sucll iIS smootliing, weighting, sJwctrum striJ>JGng, etc., ricccssary for the clctcrmination of tlic elcmcnt;d conwntration in the s;~niplc. Only the “Subroutine SIM” wltiicll is usctl tc) sirnulxtc tlic pure spcctrutn of eac11 coniponcnt is dcscrilxxl in tllis section. In ~encrating tlw pure spcctruni. if tllc ;lCtUill IWilk cllilnncl?; 0f tile S:1lllplc spectrum i\lX! not tllc s;Llllc: ;is tllosc of tllc lihxry sJJcctr:l, it is llcCCSSi\r!J to correct for tllc gziiti drift 1’4’ sllifting, one ilt il timct, c;wli lih;iry slwctrum in Sucli ;1 wily tllilt tllc Jxomincnt ~)llotol~~i~ks of tlw dcsirctl clement in tllc lilxwy ant1 tllc snmple ;lrc ;Ilignc
J
=
I’,, I’”
---
*
i
wlwrc I’,, is tllc tlcsirccl lw;ik cll;lnncl in tllc sarnlh spectrum, I,, tlw rcspcctivc Jwak illld i tllc CllilIltlCl niimbcr of tllc librxry slwctrum. ‘J’lw ;lssunlptions inherent in tllis Jwoccclurc ilrc’: (I) tlicrc is no rcli\tiVC drift in tlw first clxmncls of the lilxwy :\llcl SillllplC! SlWCtril, illld (2) 111(?drift rclationsl~ip is IillCilr. \\‘itll tllc comJ>utccl cllzuincl nulnlwrs A 1, ;111ilrr;ly r)f counts 1’1 is formed by ilssUlninff il 1inc;lr rcliltionsliip bct\WCn tllc counts for t\Vo il(lj~c’CIlt pSCUd0 clianricl llUllll~c~1~~ in tlli: il?Til~ A. Since tllC iirrX1y A is in tlic form of flXCtiOnil1 Clliln?lCl numlxxs, FLunit CllilllnCl nunilwr /(isclcfincd ;\S 1J I < /c < .‘I 1, 1 illl(l tllc! nuliih!r Of counts yk for cllil!lncl k is 0ldilind from tllc rcrhtion :
CllilIlIl~l
Y,, = <;, +
(’c--.4(A ,)(CI-A I--c,) I) I
(4)
1b I
wlicrc <.*I :incl (‘,111 rcprcscnt resJwAivcly.
tlw counts
for
tlw
pscuclo
cllanncls
rll
illltl AI+I,
A rrtr(vsis of syri thctic wixtrtrcs Jiisturcs wit11 known zmiounts of the components wcrc JxX!JXlrTly conncctccl to an RIDI, 40o-cllnnnel J~u~schcigllt nnalyacr. The spcctm of nil the stanch& were checked zinc1 in n few cnscs the impure spectra were stripped of tlic impurity ilS described above. One spectrum of cwli standnrd wr?s used ns n lilxxry spectrum ant1 the otlicr ;w a compiir~tor
Jf. P. MLSOS,
352
I). w.
I3IsI
Figure 1 illustrates how tllc spectrum of the standard for wcigllt dctcrmimltion. de&cd component is obtained from the mixed spectra by successive s’ripping. It is interesting to see from tliis I:ig. tllat tllc rcsitlual bremsstrahlung spectrum from the mixture overlaps tllc pure spectrum of plioslhorus wllicl, is a p-emitter. ‘I’llc results of tlw analysis of tlic syntlwtic mixtures using tlw stripping metlmd arc given in ‘Table I and comparwl witli the values obtained by the least-squares mctlIod. Except -__- .--
12
I ‘.‘-‘-’
‘I .‘--
___
I”‘-
.___. ___..
I---’
____
IO
._. ,_ ..- - ._._‘,..__.. -.._.,-UNKNOWN MlXTURE P94Omg Br l 2opJ No l IOOpg UNKNOWN -No
-
UNKNOWN
..‘.s.
P LIBRARY
-No
1 I _/
- Br I
(P*40mgl
2
a
08
0
I2
I6 ENERGY
20
24
28
32
(HoV)
in tlic case of potassium and mercury tllcrc is good agreement lxtwccn the values obtained using botll Inetllods. ‘I’lw large diffcrcncc bctwecn tlw results for potassium obtained from least squaws antI tliosc from thd stripping rnctliotl is probably due to an error in tllc wcigllt of potassium in tlw standard. However, tllis does not affect tlir: hsic nietlwl, Iwcausc tlic results of potassium analysis of rcplicatc llny samples seem to l~c consistent witllin cspcrimcntnl errors (see Table II). It is obvious from Tnblc I that tlw stripping metlwtl apparently yields better results for the annlysis of mercury, wliicli procluccs a y-emitter up011 iKtiViltiou with thermal neutrons, \VCill<
tllilll
tllC!
Icast-sclurwcs
111~tllOtl.
One of tllc problems cncountcrctl in tlw itctiV;~tiOll analysis of bromine obtnincd for rcsitlucs in plant materials 13 was tllilt tllc bromiIic content some of tlic samples using tllc AA-G ICiISt-SClIl;lrCS program1 was found to lw larger for tllC earlier countings tllilll tllc Values ObtiLiIlCtl litter in tllc tlCCiLy. ‘This bchvior was not, Ilowcvcr, rcflcctccl in the values ol)tninccl for soclium ancl pOti~SSiuI~1. Since the amount of bromine in tlIese sarnplcs was in tlw range of 5-20 p.p.m., it is lHYhi~l>l~ that vial ilnpuritics such ns sodium and col)pcr which produce rclativcly sllortcrlived activities than Hzl3r, can make the bromine values appear larger in tllc car11 pesticide
Amal.
Cliiw:.
Acln,
jH (13G7)
349-356
353 '1'/\I3l,EI COsf1'ARtSOS or
Tllli
LKAST-SQUAl
l’l~OCI~I>Ul
IIlcSUI.TS
1’011
OIlTAlNlcI) ,\SlJ
Till:
STI~II’I’IS~;
Till:
ASALI’SIS
01’
hll.xTUllI‘;S
..-...
_.
. ~O?lJ,MJtJCJJtS fhC*
I\‘PJIHI~~J
OJ
PJliXtJlW
ruCi~1Jf.s
0)
I~rsltIlS
C0WjXJlJCJJf.~
t/JE
_ . .
_
I’
ltJC
Sqll”Y”S
_
.._
(JJJK) _._
0.
ljr
0.02.0
100
.-
o.oro,~
O.rJlO
c-Jooc>;
Si& I< Ijr
0. IO0 I ..(f)(J O.OOJO
0.0().5.) I .S”CJl 0.00 I OS
sa I<
0. 100 J ..I’)(’
O.CJC)7.j
l)r
O.OO.!O
1.5745 0.00 I’).(
s;c
0.
0.
I00
IO.3
I ..I()(,
t’r
O.SOl’
.jo.js 0. .,nc).I
sa
0. I00
C>.OC).l7
I
(J.*jfr_5
.?
0..1”5~
3
0..7”9.3 cJ.*7X(cJ ‘J._jfJ_jO 0.j jrr, 0. _jf1.(2
4 5 0 7
I
I11
all C;\scs tllc
SpXtK~l
I ..,
I .)b
.3(,(,.S .312.4 .3.34.5 275.1
.3WLN
lS..Z_) 15.‘)’
‘5.15 13.07
14.27
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I S.C’l
I .I .faC,
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1(I.00
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15,s.;
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11.30 IS.00
I5..3” __-_-
I3.‘)0 .L
.3 1s..3 :L .jr tl;htil for
-__.
~,.00_5f’
IO
277.4 LL 312.5
Avcri1Kc
..-
I
I .a(‘)” 0.0
.
I
I<
IIK
sfrippiJJg
_
o.rJrc).j
Ijr
llrc
/JJJhP)
O.rN)_).)
_. O.O.lH7
._ ..-
CJbtaiJrcd
_~..
._0. 105.3
o.oy’
.jo.oo
Ii
THE
lJlCt~JOd
-._---..__._
sir
1’
JtSiIJ&’
fCClSllJJl’thOda
.-.
.$O.“O
Sil.
USISC
-.
iccslclts
obtrliJJc*tf
ltSJJJ&’
1JJJ6)
*
sYsT1113T1c
~11:11101)
I O..(O
3(,1.2 1.-_ ..3.)2.H-&3.) Cl1;11111cls 2S-zoo
If).‘2 ---.--1o.rn:i_
wcw
usccl
for
1.1
I I .a$)
I S.O.( :l:O.f>
tl1c co111lJiJt;1tio11
I.)..3o~:o.q
of tl1c
\vcigllts.
runs wlicn tlwse inipuritics arc not properly acwuntctl for in the hst-squares rncthod. It sl~oulcl lx pointed out that the o.gr-MeV peak of (J*JCu can hardly lx distinguishccl from tile 0.55-IMCV y-ray peak of “*13r for a visual identification of tlic traces of copper in the samlh. Since the 0.78-McV peak of H213r may lx used to sitnulAr~rtl.
ClJiJJJ.
rfcln,
38
(1367)
349-356
ate its y-ray sJwctrum in tlw successive stripping prowclurc, any contribution from H2Hr activity may Ix ~rvoiclcd. WZu to tile InCilsUrCInCnt of rcccivctl fVJm tllc c’.S.D.A., Scvcn replicates of one of tlic Ilily satnplcs C;ulfport, \vCrC irratli;~tctl, toK:ctIier wit11 cluplicatcs of sodium, JXJtiWGiuI~l and hotninc standards, in tllc rwctor for about 8 Jl at a neutron flux of illIOllt 10” n cm-2 ilftC1 sufficient cooling, in were counted, ‘I’llcsc salllJ’JCs antI tllc StilnCli~KlS see-‘. tllc same counting system as tlcscribctl Iwforc. IInalysis of tllc clata \VilS pcrformccl using botll tltc Icast-sclu;lrcs and tlic qJcctrutn stripping computer Jwogralns. Figure 2 SJIOWS tJw rcSitJU;lJ sJwc:trutn after SUcwSSiVC StriJ’Jkg of CWII Of tllct cc~rTlporIcnts,
SIMULATED
6
including tllat of tllc Iwclniiiw st;~riclwtl. It ilJ’J)l!ilrS from tllis Fig. tllirt tlwrc arc some ilnl>uritic:s wllicli can Ilnrclly Iw itlcntificcl in tlic composite spcctruin of tllc snmplc. ‘I’llc rcs\llts of tllc r?llill~SCS Of tllCsC Silllll)lCS for sodium, potassium ilIlt brorllinc c)l)ti\illCtJ using tJlc sJxxtrutl1 StriJJJlill~ mctJlotJ arc C(~ll~JX\rC!dill ‘I‘illJJC I I Wit11 tJlC WSJWcti\T! VilIUCS fro111 tllc JCilSt-S(JUilrCS JXOpXlll.
It CiLIl IJCSW11 ftX~111 ‘TilbICS J iIllping IlWtJlOd iS CIS
STI~II’I’ISC
SI’ECTItt’Sl
IS ,\CTl\‘,\‘l’IC~S
,\S.\I.\‘SIS
355
rnetl1od in idc;d cilscs. Howcvcr, if the sample cont;hw unol~servable
tlie former seems to bc impurities for whkl1 no library data can tw furnish1 for tlic Icast-squares an;Ilysis. One need not even USC the entire spcctrurn for comparison, hit instead nicasurc the arm under tlic lm-miincnt JAiotopcak of tlic striJ3pecl spcctruni much mow Jmxiscly than frown tlic ~011iJh2s sJwArum ancl coinJxwe tliis wit11 tlic Jxtk nrcn of tlic St~IIltli~d (See l:iff. 2). FurtlwrIIlOrC, if tllC iKtiV.?tiOIl JX’OdUct of tJle c]Clllcnt of illtcrcst ]1i1J3]XnS to h.2 a !VCi1k y-cniittcr (I:‘,< 0.25 Me\‘) tlic effect of Immsstralllun~ producccl by tlw p-emitters in tlic sanlJ>lc Call lx considcr;~My reclur*ctl on tlie :llli\l}*SiS of tlii?; clciiwnt l>y resorting to tlic spectrum striJ)J>inK inctl1ocl. An ;ldClctl iltl\~illlt~l~CZ of tJIis lllC!tllOCl is tllilt tlwre is no need for ilcdiVatiI1~ iIll counting tllc stnnchrcls of tllc ~llI~VillltCtl iI1IJ~iiritics hng \Vittl tJlCZSillIlJ)Ic if iL Cilt~l]OjiUC! Of t]lC li]HXry S]XXtra is ;Lvililnlllf?. *l’llC S]NX~tIUlIl striJ)Jiing IIlctlICd will be particxili~rlv ilscful for tllc ilIlillySiS c)f ill1 clclllcllt in tlic “limit-of-scIisitivity*’ t%np? in tllc presence of Illiltris intcrfc~rcIicc~. ‘I’lw activation
pml
as th?
better
Icnst-squares
tl1an
illlill~SiS
tl1c
of
latter
Immiiic
Jx2sticidcS
>*iclcls results of-scnsiti\*it>*”
Lvitll httcr
iIiStruIIicIitnl
tcclIIiiclucs.
‘I’llc
ri\llgc.
‘l‘lii:
corrects of
for
tllc
i.
tlic
c:ounts
c~lIoSc~1i
it
Iiiglicr
iS
not
StilnclilrtlS tllilt
1’ilIl
Of
wciglit
tlliln
cJuito
tllC to
for tllc
fi1Ctor
lWilk tllilt
IIC! C!.KJX_!CtCO\VlICll l‘llC
hckgrouncl
\vill
\VciglItinC:
region
1,.
in
ilccO1lllt
lilx-;irics
tllC?
StiltiSticiIl
IYJ)rMCd in
tlicr
iI
tlw
u~;ccl
rc~ioii.
in
rc~ioii
St;~tiStic*al
tllc
;tc.tivitv filCtOr
tl1:iii
flll~~tUiltiOll~
to
il
tlw
CllCBS;cIl
tllc
iii tllc
tlic: ]“ilk
il
c)nly
c-ountS iii
Jwr
tliit
lx:
in
tlIC
~~llillIll~l
\vlll Jw I00
c-ll;1nnc!l.
ill72
-:I not
of tJIc*
c~oiiIitiIil:
Sta11chrtlS
l)YcscIlt
ancl
fuiicticm
C~~)UlltS
Also of
tllc
lO\vt!l.
tllilll
IIl~:tllclcl
Kivcs
lt!sS
of CilCll sJwc*triil11 \vliic:l~ Ki1.c’s
tltcr Sillllt’ \vciKlltiiIg
C:Ictor
in
tllL*
tllc
slIoulcl InctlIo~l*
\vltcn (.‘I = 100,
x0,000
of
is
otlli!t
c~oIiiInuIiic~iItioI~.
SillIll~lC
uwtl.
“liinit-
wiiic:
iIictlIcxi
tlw
flU~tUiltiOllS 1CVClS
IiltC!r
liictlIcIcl
in tlw
ICilSt-SClU;lrC!:’
of
illS;tiIncC
rc~istcring
no
stril~]~iIiC:
0l~ti~illCYl
lm*sont
t lw
munting
for
tlic
c5Jwci;~lly
tll0sc
bvl~kl1 is niorc oftcil 11’1 = I/(‘, \VlIctrc CI is
IllOrC illlJ~C~rtilllcX2to t]lC! ilZl~l]~*siS;.13csidcs, into
I)C
tllilt
SclUilrCS, \vitlI
f;dor
flllc~tIlilti~~~IlS
r*Ollc*C*iVilbh!
Silllll~lC!. tllc
11’1
f;l\~Orill~l~
~wli~riill~
IX1Ck~:rOUIlCl
Slio\Vs
tllc! Ictnst
\~ci~lItiIi~
f;lC*tor
wciglitin~ is rcJwcsmtc(l tllr!
inatcri;~ls
tlmii
rcsultS
‘I’l1c
‘I‘llUs 11,‘1\lscCl for
times
‘I’lIcS;c!
st;ktistical
ilIlt
plant
(:oIIilxirCfs
\voi~lItinC:
Stalldi1rtlS.
l~lIi\lln~l
i1110
iirl~itraril?*
IiicIitionccl.
in
Jmxi5ion
c~01~1iti11~
Of
is ll~C!tl to t;il;c*
Si;llllJ~lC~
~lll
tllc!
illike.
I)i\*isioii of ISi~tolwS Ih:vitlopinc!nt of ‘I’llc fill~lllc~ii1l sUJq)ort rciitlcrc~tl I>?* tlw U.S. Atomic Eiicrgy Coinmission for tllis \vc)rk ;iii(l tllc fin<* ~‘OO]WTiltiOll of 3lr. I). 1;. J3Al<~l~IIi~l.of tllc L.S.I).rI., (;ulfJmrt in furnislliil/; tllc Ili1v S;iIll]~]Cs arc’ Krl!iltl> ~ipprcciatccl. ‘I’llc :lutliors ilW inclcl~tcd to I)r. i* is ~rntcfull?~ tllo
xc k llowlccl@!d.
A of
SJXXtrUll1
unknown
of the y-ray
striJ,J)ing lYlctllC1tl for ttic C~~lllJ~lltc~r-c:0~~J~l~~l iIctiViltiOl1 illl;ll~SiS sninplcs using y-m>’ sJxxAroinctry is cliscussccl. 13cforc tlic unscxxin_llJinjq is lxxfcmnetl using stzmtlarcl spectra of the ccmponcnts, cncli sJ&truni
is slnootllccl, strltisti(:itlly wciglltcd ;~nd corrwtctl for IxxkgrrJuncl. ‘1’h pllMope:lks of tllc stantl;~rcl spcctr;t ;Irc tllcn aligned wit11 tllc rcspcctive peaks of tllc sitmple spwtrurn, one ilt ;I time aftctr cca-rccting for Kilitl drift if ncccssary, ant1 tllc undcsirctl tllc cllarxtcristic spectrum c:ornp~ncnts arc strilqxxl out. After sucwssivc sui,tr;iction, of tlw tlcsircrl clcnicnt is C~Oll1l1ilr~Cl witll tliat of ttw st;Lncl;trtl to tlctcrrninc its wciglit. ‘1’11~ results cht:iinetl using tllc prcscnt inctllorl arc as f.q~ocl as tlrosc c)bt;~inctl from l)ut ill’l>C?Zlr to lx2 better wlicn i~ssunlldions IcilSt-SflUilrC!S iI1l;llt’SiS in i(lc;Il C:lSCS, irilicrctlt in tl:c IGlSt-S(lUilrC!S lTlctll0tl ilW no IonK:cr Villitl.
011
s;lwr-trt!
clc:c.rit
unc
1iitItlIcItlc
(“SlJwtrum
tl’~C~llill1tillOllS
inconnus
c:;lritctc:risticlu(:
tic l’c~l~incnt
I’illl;ll~SC!
S(III jxjitls.
1.m
rC~SUltiltS
sent
;ltissi
stril)lJing”)
lJil1’
;\c:tivittion.
c:st c-oinlxd I~~ris
clue
~3:u.x
lair
Al>rc\s il wlui ol>tcnus
spcc:trcmC~tric
soustraction cl’un lxw
Ctaloii Ia
in~~tl1Idc
~illlIlllil
Iwur
sticxc5siw, pour tics
IC
ch~tcrmiiicr 1ncJinclrcs
c’illT6S.
1% wirtl cinc ;~l;tivicrullgsir~ll~ll~tiscllc hlctllc~clc cliskuticrt, 1x4 tlc:r unlxknnntc I’rolwn untcr Vcrwcntlung cincs ;,-Sl’“ktrotnctcrs, ths mit cinctn Rccllncr Kckoppclt ist, i~llillySiC!lt wcrclcn. IhXU wwclcii \*orIwr ;o-Spektrcn clcr c:inzclncn I3cstilndtcilc niilwr untersucht untl tlann rnit dcm Sp!ktrurn dcr I’roh vcrgliclwn. Ihrcl1 itufcin;~ntIcrf~~l~:cn~k~Subtraktioncn tlcr SIwktrcn cinzclncr Elcmcntc vtrn clcnon dcr l’rolw iiiittcls clcs I
.s -I 5 0
7
x ‘J
IO I
I
I.:
’ .)
Publishing Company. in The Ncthcrlmds
Elsevlcr
Printed
349
Amsterdam
A SPEC’I-I
Rapid 1)s
y-K14
ill-c
ilVililill)lc.
Siklll])lC
instrunwntal
of
Of tllc
:llltl
part,
tllc
Of
of
results
cast
of
IX!CilUSC nature
witli
il
i\ y-ray
isotopes.
Several these
of
met.
at
CC cd.”
and
metlids
spcctruin tlie
a ~1liljOI’ with
coniph
It Wit11
IElst
few
i1
)IilVC
of
discussed
sonic
procedures
.‘-I”
hen
VillllCS,
of
tllat
spcc’tra IC’.’
if
Will
.’ in
tlIC
f down
un.wsIm ted
or the
of
nown
ON
UIlCO’l
ICVCIS
tllc
f’.
cutc’e-
stlcavn
of tlic y-r;,)’
Alifts
)I
Irltd
Of
I1 iti(:lli~
rc\*icwctl
lXC~:lltly
‘I’lic
of the
OfI
llot
Vi1ryillg
counting.
least-squares
lens
sarllplcs
is
Colll-
the
*iin
lnfi
I tl
n-
Icrns
.tt1
1). proi
&:. .a
and
preSt!nt
nxdlod,
tlie
pllotopenk
library
which
is
is pedd likely wllich
l>itSC
provisions could
witli
IInvc
viiryirlg
conditions
gain
d;lti1
illt~lOU6~1 several
but
been
use<1
tlcgrecs
in
tllc
SUCCCSS.
of
il
IlC
I
0:
,L. Nay ideal stripping have 1’ AKIJERS ,\sI) BI:A>IEI<~ Ilnvc rcportcd tlmt a “slli~clow pe;tk stringent
consiclerablc spectrum
saniplc
etc.
SpXtril
instance.
For
WllC!n
incorporates
stripping
Iaowcvcr,
is recorded
ground
ilIlt
inulticoniponcnt
cases,
rC?SUltS
tlic
S;;llllplCs
of of
tiic
ilS
from cacll
howcvcr,
prescncc
number
spwtronietry.
of
EMI~I<\-
tile
large
of
clioscn illltl
tlic
ilCtUZ\l
inetliod,
arId
wcigilt
rlletllocls.
;inalysis
of
nutnbcr
least-scluares
tllesc
y-ray
spcctronictcr
unsuspcctccl linear
Iilrgc
a
tllc
ilClliCVC.
2. It
aiial~liis tllc
y-ray
colnp~nc~~ts
clclllctlts
to
usccl’o
witll
tllc of
authors,
often
activntecl
iiiulticoliiponcnt of
cooling
difficult
ICilSt-SqU;lWS
shifts,
when
by
niorc
tllc
t Ire
Si111I)>lCS tccliniqucs
;Lfl unknown
contrilmtions
rlIiltly
ICilSt-S(lUilN?S
ant1 hSc-Iin42
il~lillyZCt1
WllC?Il
occur
tlw
niorc by
is
‘IIIC
ones
activation, spcctrul
COlll]X~lXblC
quite
mi.sturcs.
cxpcctcd
arc
Villi
arc
gain
Of
which
of
for
is tile
in
dctcrll~ini~tiorl
\vciglits
unknown
reduction
S}XXtril
ttie
SugKcStcd
cm2
arc
synthetic
of
Spcutrunl,
rnCtllodS tllc
wllicll
i~l>sc~~ccof
Ixen
niisetl is
tllc
of
(lilta of
lil)rxy
; (2)
iIViLililblC!1~‘5
sclcctcti
Wliilbk
illl;llySiS tlW
using
IitrgC! nuinbcr
;I
if
C0llCcIltriLti0ll
using
mmsurenwnt
Sc\*crill
assumptions
yield
cornlmtcr
IXlrilllll!tCrS
tcchiiiquc
ccrtai11
(f)
SillI~~)l~
tllC
tile
tllc
tllc
clerncntal
SiLIll~~IL’
IllctllOtlS
Ollly
tllC
IXlrtS:
Of
ZlllillySiS
pKlCtiCil1
Of
tW0
Ili1nlcly
cx~tll~xm21lts fitting
IX
ilCti\‘ilt~
one Of tllc scvcr;il ClClllClltS Iwcscnt in 1mrators
CillI
hI~ilSU~clll~llt
consists
spxtruni
first
;lctiviLtion
S~XXtr~~lIlCt~~
yield
f
off
sllifts. to
fIYJll1
\JC ZLffCCteCl
ilfC
ncitlicr
on
tllc
“pxling
to
correct
txttcr
a COlIIpkS
Equally
for
true
is
by
l&r&!
smootllcd tCC~llliC~UC”
gain
shifts,
SpeCtrUln
the
fact
if
tllat
StatiStiCal nor
weiglitcd
llscd
by
counting
tk
SpCtrUttl
unscrambling scatter
in
properly. previous statistics,
tllc ‘I’llC
aUtllorS, back-
results.
R71uf.
Cltinr.
Ada.
38 (1967)
349-356
.S/~ectr~m
~rocctfrrrc.s
sCri/)pirrg
‘!‘!lC
f~!!(J\Vill~
I~lulticoin!~oncnt (f) nuclitlcs
For
any
(!il,rrlry
t;ikcn
for
iwing svstctn
IllCilSUrl!
tlic
counting
s;iIiic
Icrigtll
of
xctivatctl
s>‘stcin.
tilllc
arc
of
l)ure
OlItilitl
tlicsc
iis
tlic
computer
analysis
c,f tlic
s;iIiI!)!c.
f~f il nunilwr
slwctra
of r;lt!hJ-
!)ilCkg:r~JUIll! ~!lOu!t!
.Xiltur;l!
intcrcst.
;l!So IN:
cx~ulltccl. (witli known wcigllts) of tlw clcmcnts time ant! c~orintC~~1in tllit s;ime counting slwc:trurii (JI tllc sxnii: !c*rigt!l of time i<
riltli0lIUc:!i
:~ntl tlic stancl;irtls for a known A n;itiir;\! I,;ic-k~rcJun(l
;lc.ti\*:ltcc!
/II,,..
for
wn!~!c~ycd
tlic
wliic*!~ arc
s!)cctr;l)
for any (.j)
13acli
of
tlic
S!Wl:tril,
inc*!u
tlio
fitting ii tliirtl or
l)y
rnctl1oc!
(4) Ixiscd
It’,, tllc
~ivcn
arc of
wcrc:
t;lkcIl.
sInoot!ictl tlic
s!JcctruIl~
‘I’IIC s;~lnp!cs
(2)
a~lsc,
!“““!
y-ray
rclittiOT1
II,’ , = 1 +
I/I
Ii;itur;l!
Ixlc~k~:rc~lliIc!
t!lrOug!l
;l writs
wc:i~!itct!
of
usinK
s!Jcx:trilI1l, 5 (IZltil
;i
is
!xJints
wc4gliiinC:
for i!~t~*!Ic:ll~ltlllc:! l’ollllt,
il5
tlicll using
factor, Kivcn
(f~,/C,)I<)lJ~~
I)!
(I)
tllc c3)llIlts in clw~nc!! i ilnt! nl= I’(.*I. ‘I’tw rcslwc.tivc naturrl! Ixlc:k~rount! is tllcn suld rxtctl frcltn O~C!I t jf tlw ;lllOVC Sicilll!
(,‘I
is
(5)
~~TY~pXlll
ci3cr;‘wtl
:‘S
Iiltcr.
I~rotn
tlic
sliiftctl
st;lIit!;trc!
S!wctrutn
Cl/C,,
ratios
;lrl:
counts in tlw it!1 cllmnc! ant1 (.‘,, is tllilt in tllc !w;tk cl~annc!. l;roln tlicse ratios , 11~1tlw counts in tlw rcslwc.tivc !wak c!l;mncl of tllc sampIt! slxxtrum, :I )‘-rily slw. t111m of tllat coil1!~oIlcnt is p!ncratrrc! ant! tllcn sul)tractc!t! from t!lC! conilxAtc slx:trtir~i. ‘!‘!iis gcllcrilti(JlI illlt! sucwssiw sul,tr;iction of tlllt spectra is c~wtinucd until 111~~ ~llilr;lc.tlrI~i?;tic: s!wc*tI*liti~ of tlil* c!cnsirc*c!clcllicnt is ~wc~lot! off.
rwasurcd.
\~!~cIv f I I:. tllc
‘I’IIC scalctl
U!)
grount!
as
y-WY !ly
slwtrutll
IllU!ti!>!ic~iltioIi
clcscrilml
allow.
01 tllc wit11 If.
!Jy
i\ctiViltl_!t! tllc
St;lll~!ilIX!
\vcigl:lltiIig
viSu:l!
Of
factor
till2
atid
~!SillnilliltiOll,
~ll2Ill~:llt
is
ccxmx*tc
for
il11 iln!)urit>p,
SlllOlJtllC!ll, tlic
Ixlck-
front
citlwr
sainplc clmtilillcr or
tlW
of
following xl
tllc
rcs!xxtivc
!~~lSt-SC~U~lWS
(k-lk -fl,‘
stanclard, fl~rllllllil
iI:ilIiil~izinc: for
il siiiK!c
tlw
cliffcrcnrc
~0lll!~Oll~tlt
htwccn
its
of !mrc
tile two 11)
:
.fllc) .v’lk = c)
~vhC!rC \‘lk rcpx!nts t!K! umnts in t!il! it!1 c!limtlc! clement /2 in tlic saniplc xnt! pr is tlic! !woportion
tllc: \VilS
(2) Of
t!lc
Shirdard,
.rlk
t!lOSe
of tlw St~tltli~rtl spectrum
dw
t0
of tlic
elenwnt k in tlw sample. From this prop0rtion, stantlnrd wxl the pr\r,?mctcrs usecl for activation elcnicnt in the sarnplc is computed.
tlic weight of tlic clctnent nncl counting, tlic weight
in tlic of the
‘J’lw complete computer progrrrtn usictl for the ilCtiVi\tiOn nndysis of tllC unknown SilltlI)le by tlw spectrum stripping mctlwtl is dcscrilxxl clsewlwrel~. The main pr0gr;lfll, coded in Fortrzm I\’ for nn IB!U 709_1 computer. consists of a group of sulxoutincs wliicli ni:ly lx c;tllcd in tlrc Jx0Jxr scqucncc to Jwrform the ViLlh.ls oJ)criltionS sucll iIS smootliing, weighting, sJwctrum striJ>JGng, etc., ricccssary for the clctcrmination of tlic elcmcnt;d conwntration in the s;~niplc. Only the “Subroutine SIM” wltiicll is usctl tc) sirnulxtc tlic pure spcctrutn of eac11 coniponcnt is dcscrilxxl in tllis section. In ~encrating tlw pure spcctruni. if tllc ;lCtUill IWilk cllilnncl?; 0f tile S:1lllplc spectrum i\lX! not tllc s;Llllc: ;is tllosc of tllc lihxry sJJcctr:l, it is llcCCSSi\r!J to correct for tllc gziiti drift 1’4’ sllifting, one ilt il timct, c;wli lih;iry slwctrum in Sucli ;1 wily tllilt tllc Jxomincnt ~)llotol~~i~ks of tlw dcsirctl clement in tllc lilxwy ant1 tllc snmple ;lrc ;Ilignc
J
=
I’,, I’”
---
*
i
wlwrc I’,, is tllc tlcsirccl lw;ik cll;lnncl in tllc sarnlh spectrum, I,, tlw rcspcctivc Jwak illld i tllc CllilIltlCl niimbcr of tllc librxry slwctrum. ‘J’lw ;lssunlptions inherent in tllis Jwoccclurc ilrc’: (I) tlicrc is no rcli\tiVC drift in tlw first clxmncls of the lilxwy :\llcl SillllplC! SlWCtril, illld (2) 111(?drift rclationsl~ip is IillCilr. \\‘itll tllc comJ>utccl cllzuincl nulnlwrs A 1, ;111ilrr;ly r)f counts 1’1 is formed by ilssUlninff il 1inc;lr rcliltionsliip bct\WCn tllc counts for t\Vo il(lj~c’CIlt pSCUd0 clianricl llUllll~c~1~~ in tlli: il?Til~ A. Since tllC iirrX1y A is in tlic form of flXCtiOnil1 Clliln?lCl numlxxs, FLunit CllilllnCl nunilwr /(isclcfincd ;\S 1J I < /c < .‘I 1, 1 illl(l tllc! nuliih!r Of counts yk for cllil!lncl k is 0ldilind from tllc rcrhtion :
CllilIlIl~l
Y,, = <;, +
(’c--.4(A ,)(CI-A I--c,) I) I
(4)
1b I
wlicrc <.*I :incl (‘,111 rcprcscnt resJwAivcly.
tlw counts
for
tlw
pscuclo
cllanncls
rll
illltl AI+I,
A rrtr(vsis of syri thctic wixtrtrcs Jiisturcs wit11 known zmiounts of the components wcrc JxX!JXlrT
Jf. P. MLSOS,
352
I). w.
I3IsI
Figure 1 illustrates how tllc spectrum of the standard for wcigllt dctcrmimltion. de&cd component is obtained from the mixed spectra by successive s’ripping. It is interesting to see from tliis I:ig. tllat tllc rcsitlual bremsstrahlung spectrum from the mixture overlaps tllc pure spectrum of plioslhorus wllicl, is a p-emitter. ‘I’llc results of tlw analysis of tlic syntlwtic mixtures using tlw stripping metlmd arc given in ‘Table I and comparwl witli the values obtained by the least-squares mctlIod. Except -__- .--
12
I ‘.‘-‘-’
‘I .‘--
___
I”‘-
.___. ___..
I---’
____
IO
._. ,_ ..- - ._._‘,..__.. -.._.,-UNKNOWN MlXTURE P94Omg Br l 2opJ No l IOOpg UNKNOWN -No
-
UNKNOWN
..‘.s.
P LIBRARY
-No
1 I _/
- Br I
(P*40mgl
2
a
08
0
I2
I6 ENERGY
20
24
28
32
(HoV)
in tlic case of potassium and mercury tllcrc is good agreement lxtwccn the values obtained using botll Inetllods. ‘I’lw large diffcrcncc bctwecn tlw results for potassium obtained from least squaws antI tliosc from thd stripping rnctliotl is probably due to an error in tllc wcigllt of potassium in tlw standard. However, tllis does not affect tlir: hsic nietlwl, Iwcausc tlic results of potassium analysis of rcplicatc llny samples seem to l~c consistent witllin cspcrimcntnl errors (see Table II). It is obvious from Tnblc I that tlw stripping metlwtl apparently yields better results for the annlysis of mercury, wliicli procluccs a y-emitter up011 iKtiViltiou with thermal neutrons, \VCill<
tllilll
tllC!
Icast-sclurwcs
111~tllOtl.
One of tllc problems cncountcrctl in tlw itctiV;~tiOll analysis of bromine obtnincd for rcsitlucs in plant materials 13 was tllilt tllc bromiIic content some of tlic samples using tllc AA-G ICiISt-SClIl;lrCS program1 was found to lw larger for tllC earlier countings tllilll tllc Values ObtiLiIlCtl litter in tllc tlCCiLy. ‘This bchvior was not, Ilowcvcr, rcflcctccl in the values ol)tninccl for soclium ancl pOti~SSiuI~1. Since the amount of bromine in tlIese sarnplcs was in tlw range of 5-20 p.p.m., it is lHYhi~l>l~ that vial ilnpuritics such ns sodium and col)pcr which produce rclativcly sllortcrlived activities than Hzl3r, can make the bromine values appear larger in tllc car11 pesticide
Amal.
Cliiw:.
Acln,
jH (13G7)
349-356
353 '1'/\I3l,EI COsf1'ARtSOS or
Tllli
LKAST-SQUAl
l’l~OCI~I>Ul
IIlcSUI.TS
1’011
OIlTAlNlcI) ,\SlJ
Till:
STI~II’I’IS~;
Till:
ASALI’SIS
01’
hll.xTUllI‘;S
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. ~O?lJ,MJtJCJJtS fhC*
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all C;\scs tllc
SpXtK~l
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.3(,(,.S .312.4 .3.34.5 275.1
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14.27
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I S.C’l
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11.30 IS.00
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.3 1s..3 :L .jr tl;htil for
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3(,1.2 1.-_ ..3.)2.H-&3.) Cl1;11111cls 2S-zoo
If).‘2 ---.--1o.rn:i_
wcw
usccl
for
1.1
I I .a$)
I S.O.( :l:O.f>
tl1c co111lJiJt;1tio11
I.)..3o~:o.q
of tl1c
\vcigllts.
runs wlicn tlwse inipuritics arc not properly acwuntctl for in the hst-squares rncthod. It sl~oulcl lx pointed out that the o.gr-MeV peak of (J*JCu can hardly lx distinguishccl from tile 0.55-IMCV y-ray peak of “*13r for a visual identification of tlic traces of copper in the samlh. Since the 0.78-McV peak of H213r may lx used to sitnulAr~rtl.
ClJiJJJ.
rfcln,
38
(1367)
349-356
ate its y-ray sJwctrum in tlw successive stripping prowclurc, any contribution from H2Hr activity may Ix ~rvoiclcd. WZu to tile InCilsUrCInCnt of rcccivctl fVJm tllc c’.S.D.A., Scvcn replicates of one of tlic Ilily satnplcs C;ulfport, \vCrC irratli;~tctl, toK:ctIier wit11 cluplicatcs of sodium, JXJtiWGiuI~l and hotninc standards, in tllc rwctor for about 8 Jl at a neutron flux of illIOllt 10” n cm-2 ilftC1 sufficient cooling, in were counted, ‘I’llcsc salllJ’JCs antI tllc StilnCli~KlS see-‘. tllc same counting system as tlcscribctl Iwforc. IInalysis of tllc clata \VilS pcrformccl using botll tltc Icast-sclu;lrcs and tlic qJcctrutn stripping computer Jwogralns. Figure 2 SJIOWS tJw rcSitJU;lJ sJwc:trutn after SUcwSSiVC StriJ’Jkg of CWII Of tllct cc~rTlporIcnts,
SIMULATED
6
including tllat of tllc Iwclniiiw st;~riclwtl. It ilJ’J)l!ilrS from tllis Fig. tllirt tlwrc arc some ilnl>uritic:s wllicli can Ilnrclly Iw itlcntificcl in tlic composite spcctruin of tllc snmplc. ‘I’llc rcs\llts of tllc r?llill~SCS Of tllCsC Silllll)lCS for sodium, potassium ilIlt brorllinc c)l)ti\illCtJ using tJlc sJxxtrutl1 StriJJJlill~ mctJlotJ arc C(~ll~JX\rC!dill ‘I‘illJJC I I Wit11 tJlC WSJWcti\T! VilIUCS fro111 tllc JCilSt-S(JUilrCS JXOpXlll.
It CiLIl IJCSW11 ftX~111 ‘TilbICS J iIllping IlWtJlOd iS CIS
STI~II’I’ISC
SI’ECTItt’Sl
IS ,\CTl\‘,\‘l’IC~S
,\S.\I.\‘SIS
355
rnetl1od in idc;d cilscs. Howcvcr, if the sample cont;hw unol~servable
tlie former seems to bc impurities for whkl1 no library data can tw furnish1 for tlic Icast-squares an;Ilysis. One need not even USC the entire spcctrurn for comparison, hit instead nicasurc the arm under tlic lm-miincnt JAiotopcak of tlic striJ3pecl spcctruni much mow Jmxiscly than frown tlic ~011iJh2s sJwArum ancl coinJxwe tliis wit11 tlic Jxtk nrcn of tlic St~IIltli~d (See l:iff. 2). FurtlwrIIlOrC, if tllC iKtiV.?tiOIl JX’OdUct of tJle c]Clllcnt of illtcrcst ]1i1J3]XnS to h.2 a !VCi1k y-cniittcr (I:‘,< 0.25 Me\‘) tlic effect of Immsstralllun~ producccl by tlw p-emitters in tlic sanlJ>lc Call lx considcr;~My reclur*ctl on tlie :llli\l}*SiS of tlii?; clciiwnt l>y resorting to tlic spectrum striJ)J>inK inctl1ocl. An ;ldClctl iltl\~illlt~l~CZ of tJIis lllC!tllOCl is tllilt tlwre is no need for ilcdiVatiI1~ iIll counting tllc stnnchrcls of tllc ~llI~VillltCtl iI1IJ~iiritics hng \Vittl tJlCZSillIlJ)Ic if iL Cilt~l]OjiUC! Of t]lC li]HXry S]XXtra is ;Lvililnlllf?. *l’llC S]NX~tIUlIl striJ)Jiing IIlctlICd will be particxili~rlv ilscful for tllc ilIlillySiS c)f ill1 clclllcllt in tlic “limit-of-scIisitivity*’ t%np? in tllc presence of Illiltris intcrfc~rcIicc~. ‘I’lw activation
pml
as th?
better
Icnst-squares
tl1an
illlill~SiS
tl1c
of
latter
Immiiic
Jx2sticidcS
>*iclcls results of-scnsiti\*it>*”
Lvitll httcr
iIiStruIIicIitnl
tcclIIiiclucs.
‘I’llc
ri\llgc.
‘l‘lii:
corrects of
for
tllc
i.
tlic
c:ounts
c~lIoSc~1i
it
Iiiglicr
iS
not
StilnclilrtlS tllilt
1’ilIl
Of
wciglit
tlliln
cJuito
tllC to
for tllc
fi1Ctor
lWilk tllilt
IIC! C!.KJX_!CtCO\VlICll l‘llC
hckgrouncl
\vill
\VciglItinC:
region
1,.
in
ilccO1lllt
lilx-;irics
tllC?
StiltiSticiIl
IYJ)rMCd in
tlicr
iI
tlw
u~;ccl
rc~ioii.
in
rc~ioii
St;~tiStic*al
tllc
;tc.tivitv filCtOr
tl1:iii
flll~~tUiltiOll~
to
il
tlw
CllCBS;cIl
tllc
iii tllc
tlic: ]“ilk
il
c)nly
c-ountS iii
Jwr
tliit
lx:
in
tlIC
~~llillIll~l
\vlll Jw I00
c-ll;1nnc!l.
ill72
-:I not
of tJIc*
c~oiiIitiIil:
Sta11chrtlS
l)YcscIlt
ancl
fuiicticm
C~~)UlltS
Also of
tllc
lO\vt!l.
tllilll
IIl~:tllclcl
Kivcs
lt!sS
of CilCll sJwc*triil11 \vliic:l~ Ki1.c’s
tltcr Sillllt’ \vciKlltiiIg
C:Ictor
in
tllL*
tllc
slIoulcl InctlIo~l*
\vltcn (.‘I = 100,
x0,000
of
is
otlli!t
c~oIiiInuIiic~iItioI~.
SillIll~lC
uwtl.
“liinit-
wiiic:
iIictlIcxi
tlw
flU~tUiltiOllS 1CVClS
IiltC!r
liictlIcIcl
in tlw
ICilSt-SClU;lrC!:’
of
illS;tiIncC
rc~istcring
no
stril~]~iIiC:
0l~ti~illCYl
lm*sont
t lw
munting
for
tlic
c5Jwci;~lly
tll0sc
bvl~kl1 is niorc oftcil 11’1 = I/(‘, \VlIctrc CI is
IllOrC illlJ~C~rtilllcX2to t]lC! ilZl~l]~*siS;.13csidcs, into
I)C
tllilt
SclUilrCS, \vitlI
f;dor
flllc~tIlilti~~~IlS
r*Ollc*C*iVilbh!
Silllll~lC!. tllc
11’1
f;l\~Orill~l~
~wli~riill~
IX1Ck~:rOUIlCl
Slio\Vs
tllc! Ictnst
\~ci~lItiIi~
f;lC*tor
wciglitin~ is rcJwcsmtc(l tllr!
inatcri;~ls
tlmii
rcsultS
‘I’l1c
‘I‘llUs 11,‘1\lscCl for
times
‘I’lIcS;c!
st;ktistical
ilIlt
plant
(:oIIilxirCfs
\voi~lItinC:
Stalldi1rtlS.
l~lIi\lln~l
i1110
iirl~itraril?*
IiicIitionccl.
in
Jmxi5ion
c~01~1iti11~
Of
is ll~C!tl to t;il;c*
Si;llllJ~lC~
~lll
tllc!
illike.
I)i\*isioii of ISi~tolwS Ih:vitlopinc!nt of ‘I’llc fill~lllc~ii1l sUJq)ort rciitlcrc~tl I>?* tlw U.S. Atomic Eiicrgy Coinmission for tllis \vc)rk ;iii(l tllc fin<* ~‘OO]WTiltiOll of 3lr. I). 1;. J3Al<~l~IIi~l.of tllc L.S.I).rI., (;ulfJmrt in furnislliil/; tllc Ili1v S;iIll]~]Cs arc’ Krl!iltl> ~ipprcciatccl. ‘I’llc :lutliors ilW inclcl~tcd to I)r. i
xc k llowlccl@!d.
A of
SJXXtrUll1
unknown
of the y-ray
striJ,J)ing lYlctllC1tl for ttic C~~lllJ~lltc~r-c:0~~J~l~~l iIctiViltiOl1 illl;ll~SiS sninplcs using y-m>’ sJxxAroinctry is cliscussccl. 13cforc tlic unscxxin_llJinjq is lxxfcmnetl using stzmtlarcl spectra of the ccmponcnts, cncli sJ&truni
is slnootllccl, strltisti(:itlly wciglltcd ;~nd corrwtctl for IxxkgrrJuncl. ‘1’h pllMope:lks of tllc stantl;~rcl spcctr;t ;Irc tllcn aligned wit11 tllc rcspcctive peaks of tllc sitmple spwtrurn, one ilt ;I time aftctr cca-rccting for Kilitl drift if ncccssary, ant1 tllc undcsirctl tllc cllarxtcristic spectrum c:ornp~ncnts arc strilqxxl out. After sucwssivc sui,tr;iction, of tlw tlcsircrl clcnicnt is C~Oll1l1ilr~Cl witll tliat of ttw st;Lncl;trtl to tlctcrrninc its wciglit. ‘1’11~ results cht:iinetl using tllc prcscnt inctllorl arc as f.q~ocl as tlrosc c)bt;~inctl from l)ut ill’l>C?Zlr to lx2 better wlicn i~ssunlldions IcilSt-SflUilrC!S iI1l;llt’SiS in i(lc;Il C:lSCS, irilicrctlt in tl:c IGlSt-S(lUilrC!S lTlctll0tl ilW no IonK:cr Villitl.
011
s;lwr-trt!
clc:c.rit
unc
1iitItlIcItlc
(“SlJwtrum
tl’~C~llill1tillOllS
inconnus
c:;lritctc:risticlu(:
tic l’c~l~incnt
I’illl;ll~SC!
S(III jxjitls.
1.m
rC~SUltiltS
sent
;ltissi
stril)lJing”)
lJil1’
;\c:tivittion.
c:st c-oinlxd I~~ris
clue
~3:u.x
lair
Al>rc\s il wlui ol>tcnus
spcc:trcmC~tric
soustraction cl’un lxw
Ctaloii Ia
in~~tl1Idc
~illlIlllil
Iwur
sticxc5siw, pour tics
IC
ch~tcrmiiicr 1ncJinclrcs
c’illT6S.
1% wirtl cinc ;~l;tivicrullgsir~ll~ll~tiscllc hlctllc~clc cliskuticrt, 1x4 tlc:r unlxknnntc I’rolwn untcr Vcrwcntlung cincs ;,-Sl’“ktrotnctcrs, ths mit cinctn Rccllncr Kckoppclt ist, i~llillySiC!lt wcrclcn. IhXU wwclcii \*orIwr ;o-Spektrcn clcr c:inzclncn I3cstilndtcilc niilwr untersucht untl tlann rnit dcm Sp!ktrurn dcr I’roh vcrgliclwn. Ihrcl1 itufcin;~ntIcrf~~l~:cn~k~Subtraktioncn tlcr SIwktrcn cinzclncr Elcmcntc vtrn clcnon dcr l’rolw iiiittcls clcs I
.s -I 5 0
7
x ‘J
IO I
I
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