The C-Cl bond fissions from the photolysis of CHClCCl2 at 193 nm

Article abstract of DOI:10.1063/1.476568

The photolysis of CHClCCl₂ at 193 nm was investigated by translational spectroscopy. Two distinct product translational distributions were derived for the C-Cl bond fissions. The internally excited C₂HCl₂ fragment from the main dissociation channel is shown to decompose totally to produce the Cl+C₂HCl products.

Full text of DOI:10.1063/1.476568

The C–Cl bond fissions from the photolysis of CHCl=CCl 2 at 193 nm
Yu-Jinn Lee, Ya-Rong Lee, Chih-Chiang Chou, and Shen-Maw Lin
Citation: The Journal of Chemical Physics 109, 346 (1998); doi: 10.1063/1.476568
View online: http://dx.doi.org/10.1063/1.476568
View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/109/1?ver=pdfcov
Published by the AIP Publishing
Articles you may be interested in
UV photolysis of 4-iodo-, 4-bromo-, and 4-chlorophenol: Competition between C–Y (Y = halogen) and O–H bond
fission
J. Chem. Phys. 138, 164318 (2013); 10.1063/1.4802058
Reaction of Cl with C D 4 excited to the second C–D stretching overtone
J. Chem. Phys. 126, 044315 (2007); 10.1063/1.2431368
H-atom high-n Rydberg time-of-flight spectroscopy of C–H bond fission in acrolein dissociated at 193 nm
J. Chem. Phys. 117, 7889 (2002); 10.1063/1.1510442
C–Cl bond fission, HCl elimination, and secondary radical decomposition in the 193 nm photodissociation of allyl
chloride
J. Chem. Phys. 116, 2763 (2002); 10.1063/1.1433965
Photodissociation of Cl 2 O at 248 and 308 nm
J. Chem. Phys. 107, 3337 (1997); 10.1063/1.474706
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
132.204.37.217 On: Wed, 03 Dec 2014 21:06:45

JOURNAL OF CHEMICAL PHYSICS
VOLUME 109, NUMBER 1
1 JULY 1998
LETTERS TO THE EDITOR
The Letters to the Editor section is divided into three categories entitled Notes, Comments, and Errata. Letters to the Editor are
limited to one and three-fourths journal pages as described in the Announcement in the 1 July 1998 issue.
NOTES
The C–Cl bond fissions from the photolysis of CHClvCCl at 193 nm
2
a)
Yu-Jinn Lee, Ya-Rong Lee, Chih-Chiang Chou, and Shen-Maw Lin
Institute of Atomic and Molecular Sciences, Academia Sinica and Department of Chemistry,
National Taiwan University, P.O. Box 23-166, Taipei, 10764 Taiwan
͑
Received 28 October 1997; accepted 9 December 1997͒
S0021-9606͑98͒00211-6͔
͓
Using a photofragment-translational spectroscopy ͑PTS͒,
Sato et al. recently reported their photolytic results of chlo-
roethylenes at 193 and 157 nm. Upon excitation at 193 nm,
when the P(E ) distribution ͓the dashed curve of Fig. 2͑a͔͒
t
1
ϩ
obtained from the C HCl2 spectrum accounts for only a
2
ϩ
ϩ
2
small fraction of the measured C HCl signal. Since no Cl
2
CHClvCCl is shown to undergo two primary dissociation
signal was measured in the present study, reaction ͑3͒ was
2
processes
CHClvCCl →HClϩC Cl
͑1͒
2
2
2
and
CHClvCCl →ClϩC HCl ,
͑2͒
2
2
2
and a secondary dissociation of the internally excited C HCl
2
2
via
C HCl →ClϩC HCl.
Without the actual detection of C HCl , however, their de-
͑3͒
2
2
2
ϩ
2
2
termination of reactions ͑2͒ and ͑3͒ was totally based on the
ϩ
ϩ
spectral deconvolution of the C HCl and Cl signals. This
2
will undoubtedly introduce uncertainty into the product
translational energy distributions P(E ) for these reactions
t
and the final relative product yield.
In this note we present the PTS results from a direct
ϩ
observation of the C HCl2 signal. These experiments were
2
performed with an apparatus essentially the same as that de-
2
,3
scribed elsewhere. Dissociation products after traveling a
distance of 366 mm were ionized by a 120 eV electron bom-
bardment, mass selected by a quadrupole mass filter, and
detected by a Daly ion counter. Figure 1 shows the time-of-
flight ͑TOF͒ spectra collected after averaging over 150 000–
800 000 laser shots. The circles are the experimental data
collected at a 20° beam angle with a reactant speed of 1.2
5
ϫ10 cm/s and at a laser output energy of 8–10 mJ/pulse
2
before focusing into 3ϫ1 mm at the reaction zone while the
simulated curves are calculated from the P(E ) distributions
t
depicted in Fig. 2. Simulations were performed by the for-
FIG. 1. Product TOF spectra collected at a 20° beam angle in connection
ward convolution procedure.2 As shown in Figs. 1͑a͒ and
–4
ϩ
ϩ
with the C–Cl bond fissions from CHClϭCCl2. ͑a͒ C2HCl2 , ͑b͒ C2HCl ,
ϩ
ϩ
and ͑c͒ Cl . The simulated curves are drawn: -•- for the HClϩC Cl prod-
1
͑b͒, since the spectral shape of C HCl TOF is distinctly
2
2
2
ϩ
ucts of Eq. ͑1͒, - - - for the fast C2HCl2 product of Eq. ͑2͒, -••- for the slow
Cl product of reaction ͑2͒, and ¯ for the secondary dissociation of the slow
C HCl fragment via Eq. ͑3͒.
different from that of C HCl , these ion signals cannot be
2
2
produced by the same precursor, C HCl . This is verified
2
2
2
2
0
021-9606/98/109(1)/346/2/$15.00
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
32.204.37.217 On: Wed, 03 Dec 2014 21:06:45
346
© 1998 American Institute of Physics
1

J. Chem. Phys., Vol. 109, No. 1, 1 July 1998
Letters to the Editor
347
shown in Table I is the relative product yield for reactions
,6
͑
1͒–͑3͒. It was computed5 after satisfactory fits to all other
ϩ
ϩ
ϩ
measured spectra were achieved, namely C Cl , CCl , Cl ,
and C H . The correction factor of 1ϩ␤/4 was found unim-
2
ϩ
2
portant in the present work since we detected no polarization
ϩ
ϩ
2
effect from the major ion signals of C HCl , C Cl , and
2
2
ϩ
Cl . It should be noted that because the relative yield of the
fast ClϩC HCl fragments is insignificant, equally good fit
2
2
ϩ
can be achieved for the Cl TOF spectrum ͓shown in Fig.
1
͑c͔͒ without their contribution.
In summary, we show that the C–Cl bond fission of
reaction ͑2͒ is best described by two sets of P(E ) distribu-
t
tions in spite of the fact that the fast ClϩC HCl products
2
2
accounts for less than 10% of the total product yield. These
P(E ) curves strongly suggest that the C–Cl bond fissions
t
can take place by two independent reaction routes, repre-
sented by average translational energy of 39 and 17 kcal/
mol. If the dissociation mechanism for the photoexcitation of
chloroethylenes7
–9
at ϳ200 nm is also operating for
CHClvCCl , these fast fragments can be correlated with a
2
predissociation from an initially prepared excited (␲,␲*)
state by crossing with a lower (n,␴*) state while the slow
moving products are generated from the ground electronic
state manifolds after internal conversion. In other words, the
production of the slow ClϩC HCl fragments is considered
FIG. 2. P(E ) distributions for the C–Cl bond fissions: ͑a͒ - - - for the
2
2
t
formation of the fast fragments, -••- for the slow fragments, and ͑b͒ ¯ for
to originate from a reaction route analogous to the HCl for-
mation. We therefore conclude from these experimental re-
the secondary dissociation from the slow C HCl fragment.
2
2
sults that CHClvCCl , when excited at 193 nm, dissociates
ϩ
2
sought for the unfitted C HCl signal. This is precisely the
2
predominantly from the ground state with a relative product
yield of у90%. Furthermore, results of the polarization
measurements for these major ion signals indicate that these
reaction channels are complete on a time scale longer than
the rotational period of excited species.
1
treatment used by Sato et al. However, we performed the
simulation with a different P(E ) distribution to represent
the dissociating C HCl fragment. The resultant P(E ) dis-
tributions are depicted by the dash–dot–dot and the dot
curves in Fig. 2. Table I summarizes the simulated results.
Supported by the experimental observation of the
C HCl signal, we thus obtain two separate P(E ) distribu-
tions for the C–Cl bond fissions as opposed to a single P(E )
distributions shown in the previous work. For the HCl
elimination of reaction ͑1͒, on the other hand, our P(E )
t
2
2
t
This work was supported by the National Science Coun-
cil of the Republic of China under Grant No. NSC-86-2113-
M001-032 and Chinese Petroleum Corporation.
ϩ
2
2
t
t
1
a͒
t
Author to whom correspondence should be addressed.
K. Sato, S. Tsunashima, T. Takayanagi, G. Fujisawa, and A. Yokoyama, J.
1
1
distribution is in good agreement with their work. Also
Chem. Phys. 106, 10123 ͑1997͒.
A. M. Wodtke and Y. T. Lee, J. Phys. Chem. 89, 4744 ͑1985͒.
Y. R. Lee, C. L. Chiu, and S. M. Lin, J. Chem. Phys. 100, 7376 ͑1994͒.
L. J. Butler, E. J. Hintsa, S. F. Shane, and Y. T. Lee, J. Chem. Phys. 86,
2
TABLE I. Summary of experimental results ͑E in kcal/mol͒.
3
t
4
This work
Et
Sato et al. ͑Ref. 1͒a
2051 ͑1987͒.
5
D. Krajnovich, F. Huisken, Z. Zhang, Y. R. Shen, and Y. T. Lee, J. Chem.
Phys. 77, 5977 ͑1982͒.
Process
. HClϩC Cl
͗
͘
f
͗
Et
͘
f
6
7
E. Hintsa, A. M. Wodtke, and Y. T. Lee, J. Phys. Chem. 92, 5379 ͑1988͒.
M. Umemoto, K. Seki, H. Shinohara, U. Nagashima, N. Nishi, M. Ki-
noshita, and R. Shimada, J. Chem. Phys. 83, 1657 ͑1985͒.
Y. Mo, K. Tonokura, Y. Matsumi, M. Kawasaki, T. Sato, T. Arikawa, P.
T. A. Reilly, Y. Xie, Y. A. Yang, Y. Huang, and R. J. Gordon, J. Chem.
Phys. 97, 5261 ͑1992͒.
1
14.3Ϯ2.0
р0.3
15.1Ϯ3.1
0.2
2
2
2
2
a. Fast ClϩC HCl
39.0Ϯ1.0
16.6Ϯ2.0
р0.1
у0.6
2
2
8
9
b. Slow ClϩC HCl2
19.4Ϯ2.6
5.3Ϯ1.9
0.8
2
3
. Secondary ClϩC HCl
2.9Ϯ2.0
у0.6
0.76
2
Y. Huang, Y. A. Yang, G. He, S. Hashimoto, and R. J. Gordon, J. Chem.
Phys. 103, 5476 ͑1995͒.
aThe relative product yield f is quoted with a 33% error.
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
32.204.37.217 On: Wed, 03 Dec 2014 21:06:45
1