(
)
A.I. ChichininrChemical Physics Letters 316 2000 425–432
431
1
XX
significant potential well on the excited A surface.
However, there are two facts which lead to the
agreement with experimental results for the reaction
of O) with HCl, but the calculated b2 value is
Ž
.
w x
opposite conclusion. First, the large fraction ;43%
;2.5 times lower than the experimental one 8 . We
of HqClO product energy released into translation
indicates the existence of a barrier in the exit channel
21 . There is a small barrier for hydrogen removal
feel that further improvement of the model will not
give the relation b1 fb2 observed experimentally
because of the large difference in the rotational
constants of OH and OD. Hence, the mechanism of
the formation of Cl) remains unclear.
w
x
1
XX
w
x
HOCl ™ HqClO on the excited A surface 24 ,
and there is no barrier on the ground state X 1A
X
w x
surface 5 . Second, the large isotope effect on the
w
x w
x
channel branching ratios XqClO r ClqOX ob-
served both in the present study and by Matsumi et
al. cannot be reproduced by statistical theory of
5. Summary
w x
unimolecular decay 9 . Hence, the pathway leading
The main new results obtained in the present
study may be expressed, within experimental error,
as k1 sk2 , k1a fk2a, k1b 4k2b, and k3a sk4 a. That
is, the H l D isotopic substitution does not change
the rate constant for total deactivation of O) by XCl
and the probability of the main ClqOX channel; it
changes the relative importance of ClOqX and
OqXCl channels. Also, there is no isotope effect on
the channel branching ratios for deactivation of O)
by XF.
1
X
Ž
.
to the XqClO via XOCl X A complex is in doubt.
w
x w
x
Note that the XqClO r ClqOX ratios may be
Ž
.
Ž .
explained if reactions 1b and 2b proceed via the
barrier on the excited 1A surface, if the difference in
XX
zero-point energy between HCl and DCl is taken into
account.
The third argument is brought forward in the
present study. The common statement is that reaction
1a proceeds via the ground surface 3–5 . If reac-
tion 1b proceeds via the ground surface also, chan-
nels 1a and 1b must compete. Hence, the strong
decrease of XqClO channel probability in the
deuterated case must lead to a strong increase of the
ClqOX channel probability. This increase was not
observed, hence it is tempting to think that reactions
Ž
.
w
x
Ž
Ž
.
.
Ž .
Acknowledgements
This work was supported by the Russian Founda-
tion for Basic Research through Grant 97-03-33649a.
Ž
.
Ž .
1a and 1b proceed via different surfaces.
2
(
)
4.2. On the formation of Cl P1r 2
References
The probabilities of Cl) formation in reactions
1
A.R. Ravishankara, S. Solomon, A.A. Turnipseed, R.F. War-
w x
Ž
.
ren, Science 259 1993 194.
Ž
.
Ž .
1a and 2a were measured previously by Matsumi
w x
Ž .
2
K. Schofield, J. Photochem. 9 1978 55.
w x
Ž
.
et al. 9 , using 2q1 REMPI technique at average
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Ž .
R. Schinke, J. Chem. Phys. 80 1984 5510.
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3
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.
4
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.
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.
8
A.I. Chichinin, Chem. Phys. Rep. 16 1996 635.
w x
9
Y. Matsumi, K. Tonokura, M. Kawasaki, K. Tsuji, K. Obi, J.
Ž
.
Chem. Phys. 98 1993 8330.
It was proposed that the excitation of Cl atoms
proceeds via R–E energy transfer in the exit channel
w
w
w
x
10 M. Dagenais, J.W.C. Johns, A.R.W. McKellar, Can. J. Phys.
Ž
.
54 1976 1438.
w
x
region at large distances between OX and Cl 6,9 .
Our estimate based on long-range multipole–
quadrupole interaction gives a reasonably good
x
11 V.R. Braun, L.N. Krasnoperov, V.N. Panfilov, Opt. Spec-
Ž
.
trosk. 52 1982 719.
x
Ž
.
12 A.R.W. McKellar, Can. J. Phys. 57 1979 2106.