The collinear F + H2 reaction evaluated by S-matrix propagation along delves' radial coordinate

The collinear F + H2 reaction evaluated by S-matrix propagation along delves' radial coordinate

CHEMICAL Volume 87. number 3 THE COLLINEAR EVALUATED Joxhtm PHYSICS LCITERS F + H, REACTION BY S-MATRIX PROPAGATION ALONG DELVES RADIAL COOR...

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CHEMICAL

Volume 87. number 3

THE COLLINEAR EVALUATED Joxhtm

PHYSICS LCITERS

F + H, REACTION

BY S-MATRIX

PROPAGATION

ALONG

DELVES

RADIAL

COORDINATE

RehlELT

Received 31 December 1981;in linti form 23 January 1982

The method of S-maIn\ propagsuon along Delves’ rrdlal coordmstc r IS used to evaluate ewct qu~ntum-mechmwd reacuon probablbrxs for the cohncar r+Hz rcacl~on.Thc mass asymmetry inducts Important crossmgr and rroulsd crossm&s of the wbratlonal encrg~esalong *-The rcsuhs arc m good agreement wth the standard rcfcrcnccs.

2. Consequences of the mass asymmetry

1. Introduction In previous papers [l-3] (or hypersphertcal

for the quantum-mechanical collinear method tions

Delves’ coordmates

coordtnates)

evaluation

[l-3,5].

of asymmetric

[

r, which are numencally

do not occur for symmetrtc The first apphcation collinear

reactions.

.md

(1)

as well as theoretically quantum-mechanical

studied experimentally

calculsttons

F + Hz system have been reported and Connor et al. [

[7]).

Exact

on the collmear previously

Schatz et al. [8], Adams et al. [9],

-10

Light and Walker

i

I1 1. Their results unll be For all calcula-

t~ons the hluckerman

energy surface

LEPS potenttal

____

.I

by

used as tests for the present method. No. V [

.-_---

(cf. the recent review by Ander-

son [6] and by Polanyt and Schreiber

along Delves’ angular coordtnate p

r.75:

IS to the

+ H .

This process has been extenstvely

[IO]

Tl~e most drastic change occurs tn the one-dtmension31 equation

reactton

F + Hz(v) -c FH(u’)

t J-4

IS e.y-

processes.

of the new technique

dsym-

merry, whiclt doffer from the trc~tntcn~ of synunctrtc

reacttons. This

challengmg

the consequences of rhe nws

rcx-

extension IS not trivtal. smce the massasymmetry inducts crossmgs of the vlbrational energies along Delves’ coordmate

r leas been gtven tn refs

I,? j . TIIUS for the purpose of this paper tt IS sutfi-

ctent to elaborate

of the

to sample symmetric

In the present work this method

tended to calculattons

of tl~c S-tndtrtY prop.@ton

along Delves’ radial coordmatc

of trtatomtc

reactions. So far, the applicatton has been restncted

A general dertvatton

[4]

have been adopted

“,I.,

----_

-_~--------~-------

.m.

__

..,

__.-

----

..I

----

..I

-.

c..,.,

,.

Ty. I The potcnual protile V(‘(rd)along the an&r vwuble 9 31 a constant VLIIUC air = 75 A for the system IIIH (gmA, = 0 8106 nd). The loucst lcrcls of the Jiscrcte energy spectrum

121has been used.

c, for the rextants

r + Hz(u) and products FH(u’)

+ H arc also

indicltcd.

0 009-2613/82/0000-0000/S

02.75 0 1982 North-Holland

259

~‘olun~ 87. number 3 (ci. cq (S) m rei

es [representing

[?I).

[-N/2d)a~/aJ

f vtrm9) - E,(T)]+,(T.

where V(r,gj now has an asymmerrtc prolile

(ci. fig. I)

TINS asymmetry

9) = 0. (2)

double-mmlmum induces several

processes tt IS sufiicwnt

to solve

only for the range 0 < 9 G qm.J7

sylttntetrp

wavefunction or reactant

But m the case oiasymmetrtc

properties.

an unphystcal

modes between

however,

pxtlcu1.x lxgc

m the asymptotic

potentrdl

barrier between

uct valley (cf. fig. numcncal

region ofr

where the

the reactant

and prod-

I) ma>- lead to msrablhtxs

solution

of eq. (2) (ct.. appendix

of the A m ref.

long-range exchange of vtbrais obalso ap-

A (cf. fig. 2). There,

of e4(r) and es(r) has to be

as a ktnd oi avoided crossing. Both solu-

‘Pj(r, IJI)and a5(r, g) are now located tn the

ttons

in

lo-

respectively.

energies e4(r) and E&)

the behavior

constdered same regon

however.

completely valley,

reactants and products

proach each other at r = 34

reactions the cmue range 0 < 9 < qma, has to be This ts drl-ficult,

de-

tamed

consldrred

esphcltly.

1982

it IS necessary to calcu-

late the corresponding

Both vtbrattonal

IS the skew angle oi the system). The solution (%U for the range ym.J2
= O)] are acctdentally

cahzed in the product tional

(a) For symmetric

F + Hl(u

generate *. For this situatton

Othenvlse

consequenccseq (2) e\plicttly

16 hlxch

CHEMICAL PHYSICS LETTERS

(reactant

and product

minima are not yet

separated) and therefore a direct crosstng tj forbtdden - m contrast to the situatton at r = S-9 A. Presently, we are investigating

the dynamical

consequence

of

such avotded crossings.

[?I). To overcome this problem we found IL necessary to implement

the renormaltzed

Numerov

method

of 3. Discussion of the results

ref. [ 131. (b) Asymptottcaliy

(for r + 00) the thfferent

vtbraEsact quantum

tional energies E,(T) can be assIgned to reactants or products

by localizmg

tant or product

valley,

and Ej dre tdenttlied EmI ,FoI,

the wavefuncuon respectively.

Jsymptotically

For example.

e4

as E(t-H,V’=3) and

the vlbrattonal

along tlte rxktl

coordatstc

transttion

probabthties

linear reactIon (I) have been calculated range where one Hz vIbrational or five product

vtbrattonal

state (u = 0) and four

[9], Ltght and Walker [IO]

energies e,(r) may cross

tn th? F + Hz s> stein at r - S-9x the two levels e4 (represenrmg

in fig. 3 and com-

pared with those of Schatz et al. [S]. Adams et al.

double-mmimum

r. Thus situation

for the coltn an energy

FH states (u’ = 0, I,?,3.4)

are open. The results are presented

respectively.

(c) Because oi the asymmetrIc potential

tn the reac-

IS vertlicd

(cf. fig. 2) Here

The correspondmg

and Connor et al.

potential

parameters

[I 11.

are gtven m

table 1.

FH(u’ = 3) + H) and

AU results are tn good overall agreement. ferences are presumably and conversion

constants to hfferent ehamplr,

factors which m turn lead

values of the vtbrational

thresholds.

For

tn the present work flzH = 1.008 amu,

whereas Connor et al. [ 1 I Therefore product

Some dif-

due to the use of different

] used It+., = 1.0 amu.

their vibratIonal molecule

levels of the reactant

are shifted

towards

and

higher energtes

.L‘-

pE=----

.LI.

I

1

by the dotted

the Connor

et al. thresholds

would lead to neatly perfect

.LE-

1

(as Indicated

b

‘01

*

TIT. 2. Dcpa~dcncr of the cncrpcs CJ and ES on the ndlal COordmate r ior the system THH. Note rhc avolded crossmg at r = 3-t 4 and the cmssmg at r = B-9 A.

arrows in fig. 3). Scaling to the present ones agreement of the corre-

* From 3 mathemarkd point of view the sauation corresponds to an avoIded crossmg urkss both regrons (reactant and ptoduct valley; cf. fig. I) are separated by an mtirute watl. But the actual separation between both states is smtier than 1Om8 cV and therefore

II seam

crossing 3t this potnt.

to be jumlied

10 comder

a red

CHCMCAL

Volume 87, number 3

26 hbrch 1982

PtlYSlCS LCTTERS

Table I Potcntul p3ramclcrs 3nd con~I3nrs NH21 (W Lw,) (x-1) Ro(H2) (A)

4.748 I 942

S3to p3r3mclcr (112)

0 106

D(W) (cv) P(rH) (A-‘) Ro(W (4 .%I0 psnmetcr (l-11)

6.1’7 2 219 0917 0 167

0.7-12

,,r~ (amuj

19.0

“IH (smu) roa) (i)

1 008 ‘0 1.OO’ 70

Ob) ‘m3xcj (A)

Jj ru IS the smlimg r4uc 0fr (cc rci. [‘]I ‘~1TJ plca1 propq3rron factor r,,, = r,@. cj \I.wmum \3Iuc oir. (The propag311on IO llus IJgc I vdur 1sneccs~~y IO do the asymptonc analysts of the !‘$, 3s described in rci.

[ 21 Work Is III progress to

inlpkrwn~

J

pro;ccuon slmdar 10 that used by Kuppurnmnn CI ~1. [3j. ahich uqll rcducc rhc raluc air,,, by a consldcrablc amount.)

.IS well as Ihe few points

[IO]

al. [9] arc in almost

pcrfcct

die range ofErr3ns

pubhshed

be due to the fimrc

et

with ours III

eV.

Ems

= 0.0-0.35

0 1 eV some difiercnces

by Addms

agreement

hmc

Around

=

to be noticed. rhcy nay

basis set .md 111c hmltcd

numbsr

of SecIors used in ref. [ 101. In table 1 we demonstrate respect

to the number

distmct

energres.

energy show

channels

are suflklent

even furlher

spondmg

4. Conclusion

rhe results

reactron probabilities.

Some minor

of Schatz et al. [S] haw

already

shifts

in

Iorically

closed),

1O-3

wrtlr 41 two

energy

= 0. I-18 2V corrange. The rcsulrs

energy

range only

IO

(-l/S open and G/S asyrnptoticJly to achieve

to 7 channels

convergence hater

of channels

IS dccreacd

(q/S open and 3/Z JSYIIIP-

the transItion

by only rt: 10% irom from

while Em,

1%. When the nulnber

Fg. 3 Enc~py dependence oithr reacl~on probabihr~csP$.+, ior F + H3(” = 0) -l-H(;) + H x Schstz et d [8], adzptcd iromi$.2olrci lll],nAd3mseIzIl 19].*LyhIandWalltcr, 3d3pred from lip. 5 oi ref. [ 101; o Connor et al.. adapted from fw. 2 of ref. Ill], contmuous hne: present resulrs

ch.mncls

= 0 0 I3 2V rcprcscn 1s .in

that even In rhe resonance

closed) than

E,,,,

IO a non.resonanr

propagated

prob.rbllwcs

of propagated

nedr 3 resonance

responds

the el[raordulanly

ofthe reaction

rapId convergence

their exact

probabrlrtres wlues

which

deviate range

to I.

been dls-

cussed in ref. [ 111. The results of Light and Waker

The extensionof our new techalque [I ,2I, S-matnx 261

Vohm~c 87. number 3

CHMICAL

PHYSICS LETTERS

26 March 1982

Table 1 Con~ergnce bebwlour

of ICXIIOII prob3bdittes

wth respect to the number of propagated

chmnels T p3-o

,I 3)

‘topen b,

T PI-0

T &lJ

16 l-1 12 10 9 a 7

4 4 4 1 4 4 .I

0.005 I 0.005 1 00051 0.005Z 0 0052 0.0053 0 0054

0 285 0.185 0 285 0.284 0181 0.174 0161

-

I6 I? 10 9 a 7

5 5

0.0013 0 0013 0.00 IJ 0 001-l 0.0015 0.0018

0 061 0.062 0 062 0 063 0 065 0 069

0.551 0551 0.551 0551 0549 0557

PO-o

-________ E~r~“S=0013cV

El,,,,

= 0 l-IS CV

; 5 5

0.710 0.710 0.710 0.712 0.714 0.721 0.73, 0.385 0 385 0.385 0.384 0.383 0 383

d) n IS the number of prop3:atcd chxmcls b) ,lopcn 1s the number oiopc’n chxmcls.

pr~pagauon

dong

rrc colhnear

rexuons

The resultmg F + H,(u)

-

Delves’ coordmae

reaction FH(u’)

references. Therefore

r. to asymmet-

has been tested successfully. probabllirxs

for the collinear

+ H process agree well with the we cortstder

the present work

3s the b3sIs ior 3 series of further applications

to

3syinmctrlc redctions. In particular for cdses (I.?. 112avy and hght heavy atom processes) where the conventional

rechnlques arc chftkull

The author

to apply.

thanks Dr. J. Manz ior many helpful

dicussrons and Professors S.D. Peyerirnhoff Buenker

for their contmuing

support.

and R J.

The calcula-

tlons were carried out at the Computation the Umverslry of Bonn.

Center of

References [ 11 G. HxtLc,J. bf3nz xtd J. Ram&. (1980) SOJO.

262

_I Chcm. Phys. 73

I?-] J. Ramelt,Chem Phys Lelters 74 (1980) 263 [3] A.Kuppcrmann,J A.Knyextd PJ.Dnyer.Chcm. Ph}s Letters 74 (1980) ‘57 [?I LAI. Delvcs,Nucl. Phys 9 (1959) 391; 20 (1960) 175. [S] J. Mm12 nnd J. Ramclt.Chcm. Phys. Letters 76 (1980) 337;77 (1981) 171; J.A. K~ye and A. Kuppermxtn,Chem. Phbs. Letters 77 (1981) 573; 78 (1981) 546: I. Llanz and J. Ram&, Chem. Phys. Letters 81 (1981) 179. [6] J B. Anderson. Adwn Chem. Phys 41 (1980) 1’9 171 J C. Polanyt xtd J.L. Schrciber, Fx3dq Dtscuss~ons Chem. Sot 61(1977) 267. [El G C. Schatz. J.M. Bowman and A. Kuppcrmsnn, J. Chem. Phys. 58 (1973) 4023; 63 (1975) 67% [9] J T. Adams. R L. Seth xtd E.F Hn~es. J. Chem Phj s 61(1974) 2193. [ 101 J.C. I_Ight snd R.B. Wticr, J. Chem. Phys 65 (1976) 1271. 1111 J N.L. Connor. W. Jtiubstz wd J Manz, hfol. Phys. 35 (1978) 1301;39 (1980) 799. 1l?] J.T. hluckermztn. m:Theorcr~;ll chemtstry, advances and perspecttves, Vol. 6A, ed D. Henderson (Acadetmc Press,Ncw York. 1981) pp. l-77, J. Chem. Phys. 56 (1972) ,997. J.C. Polany~and J.L. Schrelber, Chrm. Phys. Letters 29 (1974) 319. [ 131 B.R. Johnson, J. Chem. Phys 67 (1977) 3086.