Translational energy distributions of the products of the 193 and 157 nm photodissociation of chloroethylenes

Article abstract of DOI:10.1063/1.473643

The 193 and 157 nm photodissociations of three isomers of dichloroethylene (DCE) and trichloroethylene (TCE) were investigated using a technique of photofragmentation translational spectroscopy. The photofragmentation mechanisms were constructed by analyzing the time-of-flight spectra of C₂H⁺₂, Cl⁺, HCl⁺, C₂HCl⁺, and C₂Cl⁺₂ produced by electron impact of neutral photofragments. In the 193 nm photodissociation, both the HCl elimination and the C-Cl bond rupture were important for all the compounds examined. It was concluded that secondary dissociation of the vibrationally excited chlorinated vinyl radical produced by the C-Cl bond rupture was important even at 193 nm. In the 157 nm photodissociation, the mechanisms were similar to those at 193 nm for cis-DCE, 1,1-DCE, and TCE, while only the C-Cl bond rupture occurred for trans-DCE. This result suggests that the 157 nm photodissociation of trans-DCE proceeds via the direct photodissociation following the photoexcitation to the repulsive ¹nσ* state. A minor C-H bond rupture was also found in the 157 nm photodissociations of cis-DCE and TCE. On the basis of the present mechanisms, the translational energy distributions and the branching ratios were estimated for all the possible processes.

Full text of DOI:10.1063/1.473643

Translational energy distributions of the products of the 193 and 157 nm
photodissociation of chloroethylenes
Kei Sato, Shigeru Tsunashima, Toshiyuki Takayanagi, Ginji Fujisawa, and Atsushi Yokoyama
Citation: The Journal of Chemical Physics 106, 10123 (1997); doi: 10.1063/1.473643
View online: http://dx.doi.org/10.1063/1.473643
View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/106/24?ver=pdfcov
Published by the AIP Publishing
Articles you may be interested in
Photodissociation dynamics of methyl formate at 193.3 nm: Branching ratios, kinetic-energy distributions, and
angular anisotropies of products
J. Chem. Phys. 129, 194304 (2008); 10.1063/1.3020761
Photodissociation dynamics of vinyl fluoride ( C H 2 C H F ) at 157 and 193 nm : Distributions of kinetic energy
and branching ratios
J. Chem. Phys. 125, 144315 (2006); 10.1063/1.2357946
Distributions of angular anisotropy and kinetic energy of products from the photodissociation of methanol at 157
nm
J. Chem. Phys. 121, 11053 (2004); 10.1063/1.1814099
Dynamics of photodissociation of ethylene and its isotopomers at 157 nm: Branching ratios and kinetic-energy
distributions
J. Chem. Phys. 120, 10983 (2004); 10.1063/1.1740711
Competing isomeric product channels in the 193 nm photodissociation of 2-chloropropene and in the
unimolecular dissociation of the 2-propenyl radical
J. Chem. Phys. 114, 4505 (2001); 10.1063/1.1345877
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

Translational energy distributions of the products of the 193 and 157 nm
photodissociation of chloroethylenes
Kei Sato and Shigeru Tsunashima
Department of Applied Physics, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152, Japan
Toshiyuki Takayanagi, Ginji Fujisawa, and Atsushi Yokoyama
Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun,
Ibaraki 319–11, Japan
͑Received 28 October 1996; accepted 18 March 1997͒
The 193 and 157 nm photodissociations of three isomers of dichloroethylene ͑DCE͒ and
trichloroethylene ͑TCE͒ were investigated using a technique of photofragmentation translational
spectroscopy. The photofragmentation mechanisms were constructed by analyzing the time-of-flight
spectra of C2Hϩ2 , Clϩ, HClϩ, C2HClϩ, and C2Clϩ2 produced by electron impact of neutral
photofragments. In the 193 nm photodissociation, both the HCl elimination and the C–Cl bond
rupture were important for all the compounds examined. It was concluded that secondary
dissociation of the vibrationally excited chlorinated vinyl radical produced by the C–Cl bond
rupture was important even at 193 nm. In the 157 nm photodissociation, the mechanisms were
similar to those at 193 nm for cis-DCE, 1,1-DCE, and TCE, while only the C–Cl bond rupture
occurred for trans-DCE. This result suggests that the 157 nm photodissociation of trans-DCE
1
*
proceeds via the direct photodissociation following the photoexcitation to the repulsive n␴ state.
A minor C–H bond rupture was also found in the 157 nm photodissociations of cis-DCE and TCE.
On the basis of the present mechanisms, the translational energy distributions and the branching
ratios were estimated for all the possible processes. © 1997 American Institute of Physics.
͓S0021-9606͑97͒01324-X͔
I. INTRODUCTION
study photodissociations including several primary and sec-
ondary processes.28–32 Though previous workers measured
the time-of-flight ͑TOF͒ spectrum of the Cl atom to estimate
the translational energy distribution of the C–Cl bond rup-
ture, they did not measure spectrum of matching photofrag-
ments, C2H2Cl. In order to elucidate if the dissociation to
ClϩClϩCHϵCH occurs, measurements of TOF spectra for
all possible products are required.
The photodissociations of chloroethylenes have received
much attention in the field of photochemistry. Their mecha-
nisms and dynamics have been studied both
experimentally1–23 and theoretically.24–27 The energetically
possible products are shown in Fig. 1 for the UV photodis-
sociation of dichloroethylene ͑DCE͒.26,27 The three-center
͑3C͒ and four-center ͑4C͒ HCl eliminations,1–17 the H2 mo-
lecular elimination,18 and the C–Cl and C–H bond
ruptures19–23 have been confirmed to occur at 193 nm. The
HCl and H2 eliminations and the C–H bond rupture are con-
sidered to proceed via the electronic ground state. The C–Cl
bond rupture was considered to proceed via both the elec-
UV absorption spectra measured by Berry show that
chloroethylene has two absorption bands in a region between
260 and 140 nm.5 A broad absorption band at ϳ200 nm is
*
assigned to be the intervalence ␲ ←␲ transition. The pho-
todissociation initiated by this transition has been well inves-
tigated. Another absorption band at ϳ150 nm which shows a
structure is assigned to be the Rydberg 3p←␲ or
3d←␲ transition. The 157 nm absorption of cis-DCE, 1,1-
DCE, and trichloroethylene ͑TCE͒ is attributed to this Ryd-
berg transition. On the other hand, for trans-DCE the thresh-
old wavelength of the Rydberg absorption shifts to shorter
wavelength than 157 nm. In other words, the 157 nm absorp-
tion of trans-DCE is located between two absorption bands
and its cross-section is very small. The electronic state of
trans-DCE produced by the 157 nm absorption may differ
from that of the other chloroethylenes. There is no study of
the 157 nm photodissociations of chloroethylenes. From the
results of 157 nm photodissociation further information on
the photodissociation dynamics of chloroethylenes can be
obtained. In this work the photodissociations of three iso-
mers of DCE and TCE have been investigated at 193 and
157 nm using a PTS technique. The main purpose of this
1
tronic ground state and the repulsive n␴* state because the
speed distribution of Cl consists of two components.19–21 Re-
cently, Gordon and co-workers have measured the state re-
solved translational energy distributions of HCl and Cl in the
193 nm photodissociation by using velocity-aligned Doppler
spectroscopy.22,23
Acetylene is also known as a product of the UV photo-
dissociation of DCE.2–4 As the formation mechanism of this
product, dissociations to Cl2ϩCHϵCH and ClϩClϩ
CHϵCH have been proposed.9 Both processes can energeti-
cally occur even at 193 nm. Recently, He et al. confirmed Cl
to be a minor product using a resonance enhanced multi-
2
photon ionization technique.18 This result suggests that the
three-body dissociation to ClϩClϩCHϵCH occurs even at
193 nm. However, it has not been known experimentally if
such a three-body dissociation occurs. The photofragmenta-
tion translational spectroscopy ͑PTS͒ technique is useful to
J. Chem. Phys. 106 (24), 22 June 1997
0021-9606/97/106(24)/10123/11/$10.00
© 1997 American Institute of Physics
10123
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

10124
Sato et al.: Photodissociations of chloroethylenes
pulse energy was decreased by using quartz plates as a filter
for the 193 nm experiment, while the laser output was fo-
cused by a CaF2 lens (fϭ30 cm͒ to increase the fluence for
the 157 nm experiment.
The flight distance of neutral photofragments was 44 cm.
The laboratory angle between the beam axis and the detec-
tion axis was set to be ␲/9 rad. Products were analyzed by a
quadrupole mass spectrometer equipped with an electron im-
pact ionizer ͑Extrel, C50͒. The electron energy was 100 eV.
Signals at a specific mass-to-charge ratio, m/z, were pro-
cessed by a multi-channel scaler ͑Laboratory Equipment,
DN–5000͒ and a personal computer ͑NEC, PC9801DA͒. The
TOF spectra were obtained after integrating signals over
50 000–2 500 000 laser shots. The multi-channel scaler and
the laser system were synchronized by using the internal trig-
ger ͑50 Hz͒ of the excimer laser.
The velocity distributions of the reactant beams were
measured at a 0 rad laboratory angle by inserting a chopper
between the beam source and the detector. The distance be-
tween the chopper and the center of the ionizer was 25 cm.
The time width of the pulsed beam was ϳ10 ␮s. The ob-
served velocity distributions of DCE and TCE beam could be
fitted by the following function;34
2
2
n
͒ϰ exp ϪS2
Ϫ
͒2/
.
͑v vs vs ͔
͑v
v
͓
Here, S and
are the speed ratio and the mean stream
vs
FIG. 1. Energy diagram for the dissociation of DCE. The energies are cal-
velocity, respectively. Typically, S and
were 10 and 670
vs
culated based on ab initio results ͑Refs. 17,26,27͒. The energy of cis-DCE is
˙
m sϪ1 for cis-DCE at the stagnation pressure of 40 kPa.
set to be 0. For the ClϩCHClϭCH product, the upper and lower lines
˙
˙
represent the energies for Clϩcis-CHClϭCH and Clϩtrans-CHClϭCH, re-
˙
spectively. For the HϩCHClϭCCl product, the upper and lower lines rep-
˙
˙
resent the energies for Hϩtrans-CHClϭCCl and Hϩcis-CHClϭCCl, re-
III. RESULTS
spectively.
TOF spectra of C2Hϩ2 , Clϩ, HClϩ, C2HClϩ, and
C2Clϩ2 , which were produced by electron impact of neutral
photofragments, were observed. The typical TOF spectra are
shown in Figs. 2–7. The profiles of the TOF spectra were
independent of the stagnation pressure and the laser fluence.
Therefore, the effects caused by clusters of parent molecules
and/or two photon processes could be neglected under the
present experimental conditions. The TOF spectra were ana-
lyzed by employing a forward convolution method.28,33 In
the forward convolution, at first, a TOF spectrum was simu-
lated by using the measured beam velocity distribution and
an appropriately assumed relative translational energy distri-
butions of the products. Then, the simulated and observed
spectra are compared. If the observed and simulated spectra
do not fit each other, the spectrum is calculated again with a
corrected energy distribution. This procedure is repeated un-
til the simulated spectrum fits well with the observed one.
Details of the analysis in each case are given below.
work is to elucidate the overall photodissociation mecha-
nisms of chloroethylenes.
II. EXPERIMENT
The apparatus used in the present PTS experiment con-
sisted of a rotatable beam source and a fixed detector. The
apparatus was essentially the same as that described
elsewhere.33 Cis-DCE ͑Aldrich, 97%͒, trans-DCE ͑Tokyo
Kasei, 99%͒, 1,1-DCE ͑Aldrich, 99%͒, and TCE ͑Tokyo
Kasei, 99%͒ were used after being degassed at 77 K. A mix-
ture gas of chloroethylene ͑20–30% in Ar͒ was obtained by
bubbling Ar through liquid chloroethylene whose tempera-
ture was controlled to set the vapor pressure to be 8 kPa. The
mixture gas was expanded into a main vacuum chamber
through a nozzle kept at 490 K. The stagnation pressure was
set to be 27–40 kPa. The pressure of the main chamber was
10 ␮Pa when the beam was introduced.
An excimer laser ͑Lambda Physik, LPF200͒ was used as
a photodissociation laser. The laser beam was crossed at
right-angles with the molecular beam. The size of laser spot
was 5ϫ15 mm at the interaction region. The pulse energies
measured by a Joule meter ͑Gentec, ED–500͒ were 50 and
70 mJ for the ArF ͑193 nm͒ and F2 ͑157 nm͒ lasers, respec-
tively. Irradiation was carried out at several laser fluences in
order to measure the power dependence of TOF spectra. The
A. 193 nm photodissociation of cis-DCE, trans-DCE
and TCE
In the 193 nm photodissociation of cis-DCE, signals of
the products were observed as HClϩ, C2HClϩ, Clϩ, and
C2Hϩ2 . The TOF spectra are shown in Fig. 2. The signals of
HClϩ ͑Fig. 2a͒ and C2HClϩ ͑Fig. 2b͒ should be due to the
fragments HCl and C2HCl, respectively, from the following
HCl elimination:
J. Chem. Phys., Vol. 106, No. 24, 22 June 1997
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

Sato et al.: Photodissociations of chloroethylenes
10125
FIG. 2. TOF spectra in the 193 nm photodissociation of cis-DCE. Lines are
the simulated curves. Numbers shown in the figure correspond to the reac-
tion numbers ͑see text͒.
FIG. 3. TOF spectra in the 193 nm photodissociation of 1,1-DCE. Lines are
the simulated curves. Numbers shown in the figure correspond to the reac-
tion numbers ͑see text͒. For spectrum ͑d͒, the curve for reaction ͑2͒ was
simulated according to the dashed region of Fig. 9c ͑see text͒.
C2H2Cl2ϩh␯→ HClϩC2HCl.
͑1͒
tive ionization of C2H2Cl. At first, we estimated the transla-
tional energy distribution for reaction ͑2͒ by fitting the Clϩ
spectrum only with reactions ͑1͒ and ͑2͒. Then, the C2H2Cl
spectrum was simulated by using the translational energy
distribution for reaction ͑2͒ and assuming the momentum
matching between Cl and C2H2Cl. The result of the simula-
tion is shown in Fig. 6. The matching between the observed
and calculated spectra is poor. Therefore, all spectra cannot
be explained consistently only with reactions ͑1͒ and ͑2͒.
There are two possibilities to explain all TOF spectra: One is
the addition of Cl2 elimination reaction:
Both spectra could be fitted by using the translational energy
distribution shown in Fig. 8a under the assumption of the
linear momentum conservation between HCl and C2HCl.
The simulated curves are also shown in Figs 2a and 2b as
dotted lines. The momentum matching between the HCl and
C2HCl fragments verifies the validity of this assignment.
Since Clϩ ions are produced by electron bombardment
of HCl at 100 eV,33 the HCl fragment from reaction ͑1͒
should contribute to the Clϩ spectrum shown in Fig. 2c. If all
Clϩ ions come from the dissociative ionization of HCl, the
Clϩ and HClϩ TOF spectra should be identical. However,
the Clϩ spectrum is different from the HClϩ spectrum as
shown in Figs. 2a and 2c. Therefore, other processes also
contribute to the Clϩ TOF spectrum. A possible candidate is
Cl atoms from the following C–Cl bond rupture:
C2H2Cl2ϩh␯→ Cl2ϩC2H2 .
If this reaction occurred, the Cl2 fragment should be ob-
served as Clϩ2 .35 However, no Clϩ2 signal observed even at
the electron energy of 40 eV. Therefore, this Cl2 elimination
is a minor process. The other possibility is the addition of
secondary C–Cl bond rupture following reaction ͑2͒:
C2H2Cl2ϩh␯→ ClϩC2H2Cl.
͑2͒
Although the primary ions of C2H2Cl were not observed, the
C2H2Cl fragment may appear as the C2Hϩ2 ion by dissocia-
CHϭCHCl→ CHϵCHϩCl.
͑3͒
˙
J. Chem. Phys., Vol. 106, No. 24, 22 June 1997
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

10126
Sato et al.: Photodissociations of chloroethylenes
FIG. 4. TOF spectra in the 157 nm photodissociation of cis-DCE. Lines are
the simulated curves. Numbers shown in the figure correspond to the reac-
tion numbers ͑see text͒.
FIG. 5. TOF spectra in the 157 nm photodissociation of trans-DCE. Lines
are the simulated curves. Numbers shown in the figure correspond to the
reaction numbers ͑see text͒.
determined by using the ͑Clϩ)/͑HClϩ) ratio of HCl mass
This reaction is energetically possible as described later.
Then, we analyzed the Clϩ and C2Hϩ2 spectra using reaction
͑3͒ in addition to reactions ͑1͒ and ͑2͒.
signal, which has been determined to be three under the
present experimental condition.17 Since all CHϭCHCl radi-
˙
In this analysis, the C2Hϩ2 signal, I26(t), was assumed to
consist of two components;
cals dissociate, the yields of Cl from reactions ͑2͒ and ͑3͒
should be the same. Under this restriction, c4 and c5 can be
determined. The Clϩ and C2Hϩ2 spectra are fitted well by
choosing appropriate translational energy distributions for
reactions ͑2͒ and ͑3͒ as shown in Fig. 2.
The translational energy distributions for reactions ͑2͒
and ͑3͒ are shown in Figs. 9a and 10a, respectively. The
translational energy distribution for reaction ͑2͒ shows two
peaks corresponding to the two peaks in the TOF spectrum.
The first peak is around 0 kJ molϪ1 and the distribution de-
creases monotonically with increasing energy. This tendency
is similar to the distribution for the C–Cl bond rupture on the
ground electronic state.33 On the other hand, the second peak
is away from zero. This indicates that the C–Cl bond rupture
occurs along the repulsive potential energy surface. There-
fore, it is reasonably concluded that the C–Cl bond rupture
I26 t͒ϭc f t͒ϩc f t͒,
͑
͑
͑
1
2
2
3
˙
where f2(t) and f3(t) represent curves for CHϭCHCl pro-
duced by reaction ͑2͒ and C2H2 produced by reaction ͑3͒,
respectively, and c1 and c2 are fractions of these compo-
nents. When the f2(t) component is included, the simulated
curve for C2Hϩ2 shows a sharp peak at ϳ300 ␮s and is not
fitted to the observed spectrum like the simulated curve in
˙
Fig. 6. This indicates that all CHϭCHCl radicals dissociate
via reaction ͑3͒. Thus, c1 is 0. The Clϩ signal, I35(t), con-
sists of three components;
I35 t͒ϭc fЈ t͒ϩc fЈ t͒ϩc fЈ t͒,
͑
͑
͑
͑
3
4
5
1
2
3
where f1Ј(t), f2Ј(t), and fЈ3(t) represent curves for HCl pro-
duced by reaction ͑1͒, Cl produced by reaction ͑2͒, and Cl
produced by reaction ͑3͒, respectively. Parameter, c3, can be
occurs competitively via two different reaction paths, i.e.,
1
*
processes via the n␴ potential energy surface and the vi-
J. Chem. Phys., Vol. 106, No. 24, 22 June 1997
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

Sato et al.: Photodissociations of chloroethylenes
10127
FIG. 6. C2Hϩ2 spectrum for the 193 nm photodissociation of cis-DCE, which
is analyzed by considering only reactions ͑1͒ and ͑2͒. A dotted line is the
simulated curve.
brationally excited ground state, as has been suggested by
previous workers.19–23
˙
It is energetically possible that all CHϭCHCl radicals
dissociate spontaneously by reaction ͑3͒. In Fig. 9a, the total
FIG. 8. Translational energy distributions for the HCl elimination, reaction
͑1͒, for the 193 nm photodissociation of cis-DCE ͑a͒, trans-DCE ͑b͒, 1,1-
DCE ͑c͒, and TCE ͑d͒ and for the 157 nm photodissociation of cis-DCE ͑e͒,
trans-DCE ͑f͒, 1,1-DCE ͑g͒, and TCE ͑h͒.
available energy for reaction ͑2͒, E1 ͑242 kJ molϪ1), and the
˙
maximum translational energy permitted for CHϭCHCl to
proceed reaction ͑3͒, E2 ͑196 kJ molϪ1), are also shown as
solid and dotted arrows, respectively. Here, E2 is given by
the difference between E1 and the C–Cl bond energy of
˙
action ͑2͒ is lower than E2, all radicals can dissociate ener-
getically.
CHϭCHCl. Since the maximum translational energy for re-
Since the TOF spectra for trans-DCE and TCE were
similar to those for cis-DCE, analysis for trans-DCE and
TCE was performed in the similar manner as done for cis-
DCE. The translational energy distributions for trans-DCE
are shown in Figs. 8b, 9b, and 10b for reactions ͑1͒, ͑2͒, and
͑3͒, respectively. In the case of TCE, C2HClϩ and C2H2ϩ
should read as C2Clϩ2 and C2HClϩ, respectively. The trans-
lational energy distributions for TCE are shown in Figs. 8d,
9d, and 10d for reactions ͑1͒, ͑2͒ and ͑3͒, respectively. As
shown in Fig. 9d, a small part of the product of reaction ͑2͒
has higher translational energy than the dissociation limit,
E2. In the present simulation, this component was assumed
not to dissociate by reaction ͑3͒.
B. 193 nm photodissociation of 1,1-DCE
For 1,1-DCE, the HClϩ signal in Fig. 3a is attributed to
HCl from reaction ͑1͒. The translational energy distribution
for reaction ͑1͒ obtained from the fitting of the HClϩ spec-
trum is shown in Fig. 8c. A line numbered 1 in Fig. 3b shows
a curve simulated by using energy distribution for reaction
͑1͒ estimated from HClϩ spectrum. The C2HClϩ spectrum
͑Fig. 3b͒ contains a slow component resulting from a chan-
FIG. 7. C2Hϩ2 spectrum for the 193 nm photodissociation of 1,1-DCE,
which is analyzed by considering only reactions ͑1͒ and ͑2͒. A dotted line is
the simulated curve.
J. Chem. Phys., Vol. 106, No. 24, 22 June 1997
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

10128
Sato et al.: Photodissociations of chloroethylenes
FIG. 9. Translational energy distributions for the C–Cl bond rupture, reac-
tion ͑2͒, for the 193 nm photodissociation of cis-DCE ͑a͒, trans-DCE ͑b͒,
1,1-DCE ͑c͒, and TCE ͑d͒ and for the 157 nm photodissociation of cis-DCE
͑e͒, trans-DCE ͑f͒, 1,1-DCE ͑g͒, and TCE ͑h͒. For dotted line in Figs. 7c
and 7g, see text.
FIG. 10. Translational energy distributions for the secondary dissociations
of chlorinated vinyl radicals, reaction ͑3͒, for the 193 nm photodissociation
of cis-DCE ͑a͒, trans-DCE ͑b͒, and TCE ͑d͒ and for the 157 nm photodis-
sociation of cis-DCE ͑e͒, trans-DCE ͑f͒, and TCE ͑h͒. For the case of
1,1-DCE ͑c and g͒, the secondary dissociation is reaction ͑3H) instead of
reaction ͑3͒.
˙
nel other than reaction ͑1͒. This slow component can be at-
3 ͒
H
͑
CH2ϭCCl→ HϩCHϵCCl.
˙
tributed to a secondary dissociation, CH2ϭCCl→HϩCH
ϵCCl, as described below.
A possible source of the Clϩ ions is the dissociative
ionization of HCl from reaction ͑1͒ and the ionization of the
Cl atoms from reaction ͑2͒. Since the C–Cl bond dissocia-
Although no signal for H produced by reaction ͑3H) could be
detected because of the high background at m/zϭ1, this sec-
ondary reaction should be the cause of the decrease in the
C2Hϩ2 signal at long flight time. The C2Hϩ2 spectrum is at-
tion energy of the CH2ϭCCl radical ͑238 kJ molϪ1) is larger
˙
than the C–H bond dissociation energy ͑169 kJ molϪ1), the
˙
tributed to CH2ϭCCl which did not dissociate.
˙
C–Cl bond rupture of the CH2ϭCCl radical is energetically
The translational energy distribution for reaction ͑2͒
unfavorable. Therefore, the Clϩ spectrum can be fitted only
with reactions ͑1͒ and ͑2͒. The translational energy distribu-
tion for reaction ͑2͒ obtained from the Clϩ spectrum is
shown in Fig. 9c with a solid line. Since the production of
˙
with stable CH2ϭCCl and Cl fragments can be obtained
from the C2Hϩ2 spectrum. Subtracting this distribution
from the total distribution for reaction ͑2͒, we can get the
distribution with the unstable CH2ϭCCl and Cl fragments.
This distribution is shown in Fig. 9c with a dotted line. The
CH2ϭCCl fragment with the translational energy release less
˙
˙
C2H2 from the C–Cl bond rupture of the CH2ϭCCl radical
˙
can be neglected as described above, the possible source of
C2Hϩ2 is only CH2ϭCCl from reaction ͑2͒. By using the
than E2 ͑89 kJ molϪ1), which is indicated as a dotted arrow
in Fig. 9c, has sufficient internal energy to dissociate spon-
taneously through reaction ͑3H). Since the maximum trans-
lational energy of the dotted line in Fig. 9c is lower than
E2, reaction ͑3H) can occur energetically. A curve for the
slow component of the C2HClϩ spectrum was simulated us-
ing the energy distribution of the dotted line in Fig. 9c and is
shown in Fig. 3b with a line numbered by 3H .
˙
energy distribution for reaction ͑2͒ obtained from Clϩ spec-
trum, a curve for C2Hϩ2 as simulated. The simulated curve is
shown in Fig. 7. Although a fast peak of the C2Hϩ2 spectrum
is reproduced by the simulated curve, the slow part of the
spectrum does not fit and is lower than the simulated curve.
˙
Slow CH2ϭCCl must be vibrationally excited and can dis-
sociate via the secondary dissociation:
J. Chem. Phys., Vol. 106, No. 24, 22 June 1997
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

Sato et al.: Photodissociations of chloroethylenes
10129
TABLE I. Mean translational energies in units of kJ molϪ1. Numbers in
brackets represent errors for the mean energies. For reaction numbers, see
text.
C. 157 nm photodissociation
In the case of the 157 nm photodissociation of cis-DCE,
the spectra could be analyzed by the similar mechanism as
the case of 193 nm. TOF spectra are shown in Fig. 4. The
translational energy distributions for reactions ͑1͒, ͑2͒, and
͑3͒ obtained in this manner are shown in Figs. 8e, 9e, and
10e, respectively. As shown in Fig. 4b, the C2HClϩ spec-
trum contains a slow component which could not be fitted
only with reaction ͑1͒. This slow component is attributed to
either the dissociation to HϩC2HCl2 or HϩClϩC2HCl. The
TOF spectrum could be reproduced by simulations for both
cases. However, for HϩC2HCl2, the mean translational en-
ergy estimated from the simulation much exceeded the total
available energy. Thus, the slow component of the C2HClϩ
spectrum is assigned to the product of the stepwise dissocia-
tion;
Reactions
1
2
3
4
5
193 nm
cis
trans
1,1
TCE
157 nm
cis
trans
1,1
63͑8͒
63͑8͒
75͑8͒
63͑13͒
69͑11͒
84͑13͒
101͑14͒
81͑11͒
28͑8͒
21͑8͒
8͑4͒
•••
•••
•••
•••
•••
•••
•••
•••
22͑8͒
63͑13͒
•••
79͑8͒
63͑13͒
101͑15͒
194͑32͒
113͑20͒
98͑16͒
36͑13͒
39͑12͒
15͑10͒
47͑13͒
25͑21͒
•••
•••
21͑8͒
•••
•••
TCE
25͑21͒
21͑8͒
the number of the laser shots, P is the pulse energy of the
dissociation laser, ␴ is the maximum ionization cross-section
of the product,33 and f(␪) is the angular-distribution function
of the product in the laboratory frame and is calculated by
assuming the isotropic recoil of the products in the center-
of-mass frame. The product with higher anisotropy param-
eter, ␤, is detected with higher sensitivity by a factor of ͑1ϩ
␤/4͒.32 Thus, the correction for this effect was also carried
out by using the measured ␤ values for dissociations at 193
nm.19 Since ␤ was unknown for the 157 nm photodissocia-
tions, the deviation of ␾ caused by this effect was treated as
an error.
˙
CHClϭCHClϩh␯→ HϩCClϭCHCl,
˙
͑4͒
͑5͒
CClϭCHCl→ CClϵCHϩCl.
Unfortunately, no H signal attributed to reaction ͑4͒ could be
detected because of the high background at m/zϭ1. The
translational energy distributions for reactions ͑4͒ and ͑5͒
were a assumed to be exponential curves which are typical
distribution for a simple bond rupture with no exit barrier.
Analysis for TCE could be performed in a similar manner as
the case of cis-DCE. The translational energy distributions
for TCE are shown in Figs. 8h, 9h, and 10h for reactions ͑1͒,
͑2͒, and ͑3͒, respectively.
TOF spectra for 1,1-DCE were consistently analyzed by
employing the same mechanism considered for 193 nm pho-
todissociation of 1,1-DCE. The translational energy distribu-
tions for reactions ͑1͒, ͑2͒, and ͑3H) are shown in Figs. 8g,
9g, and 10g, respectively.
In the case of trans-DCE, the ion signals of the frag-
ments were observed only for C2Hϩ2 and Clϩ as shown in
Fig. 5. The signal intensities for HClϩ and C2HClϩ were too
low to observe the TOF spectra. This suggests that the HCl
elimination, reaction ͑1͒, is a minor process. The spectra for
Clϩ ͑Fig. 5a͒ and C2Hϩ2 ͑Fig. 5b͒ are attributed to the prod-
ucts of reactions ͑2͒ and ͑3͒. The distributions for reactions
͑2͒ and ͑3͒ are shown in Figs. 9f and 10f, respectively. As
shown in Fig. 9f, a small part of the product of reaction ͑2͒
has higher translational energy than the dissociation limit,
E2. In the present simulation, this component was assumed
not to dissociate by reaction ͑3͒.
IV. DISCUSSION
A. Secondary dissociation of chlorinated vinyl radical
˙
As discussed in the previous section, the CHϭCHCl
produced by reaction ͑2͒ of 1,2-DCE dissociates to
CHϵCHϩCl. However, CHϭCHCl is energetically possible
˙
to dissociate not only to CHϵCHϩCl but also to
CHϵCClϩH at 193 nm as shown in Fig. 1. Using the simple
RRK calculation,36 the rate constants were evaluated to be 1
ϫ1013 and 4ϫ1010 sϪ1 for the C–Cl and C–H bond rupture
˙
of CHϭCHCl, respectively, under the assumption that all the
available energy for reaction ͑2͒ is partitioned into the ro-
TABLE II. Relative yields of products.
Reactions
1
2
3
4
5
193 nm
cis
trans
1,1
TCE
157 nm
cis
trans
1,1
D. Mean translational energy and branching ratio
0.3
0.5
0.5
0.2a
0.7
0.5
0.5
0.8a
0.7
0.5
ϳ0
ϳ0
ϳ0
ϳ0
ϳ0
ϳ0
ϳ0
ϳ0
The mean translational energies and the relative yields of
the products are listed in Table I and Table II, respectively.
The relative yield, ␾, can be calculated from the total inten-
sity for the product signal, I, by the following equation;32,33
0.1
0.76a
0.2a
0.7a
ϳ1
0.5a
0.7a
0.7a
0.95a
0.3a
0.7a
0.1a
0.1a
ϳ0
ϳ0
ϳ0
ϳ0
ϳ0
I
0.5a
0.2a
␾ϭ
,
TCE
0.1a
0.1a
QNP␴f ␪͒ 1ϩ␤/4͒
͑
͑
aRelative yields which have errors of 33% since the anisotropy parameters
are unknown. For reaction numbers, see text.
where Q is the normalization factor and is determined by
setting the sum of ␾ for the primary products to be 1, N is
J. Chem. Phys., Vol. 106, No. 24, 22 June 1997
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

10130
Sato et al.: Photodissociations of chloroethylenes
˙
vibrational energies of CHϭCHCl. This result shows that the
C–Cl bond rupture mainly occurs in accordance with the
experimental results. Acetylene is produced by the secondary
˙
dissociation of CHϭCHCl radical. On the other hand, the
˙
CH2ϭCCl produced by reaction ͑2͒ of 1,1-DCE was shown
to dissociate to HϩCHϵCCl. Thus, acetylene is a minor
product in the photodissociation of 1,1-DCE. This conclu-
sion is also supported by the previous experimental results.
Ausubel and Wijnen2–4 and Moss et al.9 have reported that
the relative yield of acetylene in the UV photodissociation of
1,2-DCE is much higher than that of 1,1-DCE. In addition,
He et al. have described that the relative yield of the H atom
in the 193 nm photodissociation of 1,1-DCE is 3.8 times as
large as that of cis-DCE.13 He et al. considered that H atom
was produced by the C–H bond rupture of DCE. However,
taking into account the present results, H atom formed in the
photodissociation of 1,1-DCE is produced not only by the
C–H bond rupture of 1,1-DCE but also by the secondary
˙
dissociation of CH2ϭCCl. The secondary dissociation of
chlorinated vinyl radical produced by reaction ͑2͒ is impor-
tant even at 193 nm.
As shown in Fig. 10, the peaks of the translational en-
ergy distributions are away from zero for the secondary
C–Cl bond rupture, reaction ͑3͒, while they are close to zero
for the secondary C–H bond rupture, reaction ͑3H). The non-
zero peak for reaction ͑3͒ should not be caused by the exit
barrier of the electronic potential energy surface because the
activation energy for the reverse reaction, ClϩC2H2, is
nearly equal to zero.37 This is probably due to the centrifugal
FIG. 11. Schematic diagram of the C–Cl bond rupture. VR represents chlo-
rinated vinyl radical. I, II, and III represents the initial excited state for the
193 nm photodissociation, the 157 nm photodissociation of chloroethylenes
other than trans-DCE, and the 157 nm photodissociation of trans-DCE,
respectively.
barrier for the Cl–C2H2 system. A part of C2H2Cl is pro-
1
*
duced by the reaction via the repulsive n␴ state. So
C2H2Cl would be excited not only for the translational en-
ergy but also for the rotational energy. For the rotationally
excited system the peak of the translational energy distribu-
tion of the product is known to not come at zero due to the
centrifugal barrier.38 Thus, the peaks of the energy distribu-
tions for reaction ͑3͒ are away from zero. For the photodis-
sociation of 1,1-DCE, the peak of the translational energy
distribution of reaction ͑3H) was at zero as shown in
Fig. 10c. The centrifugal barrier for reaction ͑3H) will be
lower than that for reaction ͑3͒ because the reduced mass
of the H–C2HCl system is much smaller than that of the
Cl–C2H2. Thus, the peak for the reaction ͑3H) is located at
lower energy than that for reaction ͑3͒.
1
*
␲␲ state shown in Fig. 11 as I by the 193 nm absorption.
1
*
Then, DCE in the ␲␲ state dissociates via the repulsive
1
*
n␴ state and/or the electronic ground state. For the disso-
ciation via the repulsive state, the relative translational en-
ergy of products should be high.
For cis-DCE, 1,1-DCE, and TCE, the 157 nm absorption
is assigned to the Rydberg 3p←␲ transition.5 Though the
initial electronic states are different for the 193 and 157 nm
photodissociations, the peaks of the translational energy dis-
tributions for the fast Cl component are close each other as
shown in Fig. 9. This result can be explained by the reaction
scheme described below. These chloroethylenes are excited
1
to the ␲3p state shown as II in Fig. 11 by the 157 nm
absorption. The absorption spectrum for these compounds
B. Mechanism for the 157 nm photodissociation
shows a structure at ϳ157 nm. Thus the lifetime of chloro-
For the 193 nm photodissociation, the translational en-
ergy distributions for reaction ͑2͒ has two peaks as shown in
Figs 9a–9d. This result could be consistently explained by
the mechanism proposed by previous workers, i.e., reaction
͑2͒ occurs via two processes:19–23
1
ethylenes in the ␲3p state may be long enough to undergo
1
*
to the ␲␲ state via the internal conversion. Chloroethyl-
1
1
*
*
enes in the ␲␲ state can dissociate via the n␴ state or
the ground state similarly to the 193 nm photodissociation.
In this reaction scheme, the C-Cl bond rupture for 157 nm
1
*
also proceeds via the crossing point between the ␲␲ and
1
*
n␴ states. Umemoto et al. suggested that the mean trans-
lational energy is determined mainly by the energy differ-
ence between the product and the crossing point.19 Since the
C–Cl bond rupture proceeds via the same crossing point for
the 193 and 157 nm photodissociations, the peaks of the
where superscript ‡ represents the vibrationally excited mol-
ecule in the electronic ground state. Figure 11 shows a sche-
matic energy diagram for reaction ͑2͒. DCE is excited to the
J. Chem. Phys., Vol. 106, No. 24, 22 June 1997
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

Sato et al.: Photodissociations of chloroethylenes
10131
1
*
translational energy distributions for the fast Cl component
are close each other.
As for trans-DCE, the peak for the fast Cl component
obtained at 157 nm is located at a much higher energy than
petition of the internal conversions of the ␲␲ -state chlo-
roethylene to the electronic ground state with that of the
n␴ state.
For each chloroethylene, the mean translational energy
1
*
that obtained at 193 nm as shown in Fig. 9f. This result
for the HCl elimination obtained at 193 nm is nearly equal to
that obtained at 157 nm as listed in Table I. Sato et al. have
also reported that the mean translational energies for the in-
frared multiphoton dissociation and the UV photodissocia-
tion of 1,1-DCE are nearly the same.15 That is to say, the
mean translational energy is not sensitive to the excitation
energy. The mean vibrational energy of HCl is also known to
not be sensitive to the excitation energy.5 These results are
consistently explained as described below. The mean trans-
lational energy, E , is known to be represented by the fol-
1
*
suggests that the initial energy of DCE in the n␴ state is
1
*
higher than the crossing point between the n␴ and
1
*
␲␲ states. The absorption spectrum is structureless at
around 157 nm.5 This means that the excited-state trans-
DCE produced by the 157 nm absorption has a shorter life-
time than 1␲3p-state chloroethylene. In addition, the 157 nm
absorption for trans-DCE is located between the absorption
*
bands for the ␲ ←␲ and 3p←␲ transitions and its cross-
5
*
section is very small. The absorption for the ␴ ←n transi-
͗
͘
t
tion of the C–Cl bond is known to broaden at ϳ150 nm.32
lowing equation;25
Therefore, the upper state of the 157 nm absorption of trans-
E ϭaEexcϩbEb ,
͑6͒
͗
͘
1
t
*
DCE is considered to be the repulsive n␴ state shown as
III in Fig. 11. The peak energy (ϳ 280 kJ molϪ1) is close to
the available energy (E1ϭ387 kJ molϪ1) indicated as solid
arrow in Fig. 9f. Such a distribution is similar to that for the
C–Cl bond rupture from CBrF2 –CHClF which is the direct
where Eexc and Eb represent the excess energy at the transi-
tion state and the exit-barrier energy, respectively. Constant
a is determined by a statistical factor, while constant b is
determined from the characteristics of the potential energy
surface in the exit channel.25 The peaks of the translational
energy distributions for the HCl eliminations are not at zero
as shown in Fig. 8. This indicates that the translational en-
ergy distributions for the HCl eliminations are influenced by
the exit barrier. For the reaction with the exit barrier, the
aEexc term in Equation ͑6͒ should be relatively small in com-
parison with the second term in Equation ͑6͒ because Eexc
are mainly partitioned into the ro-vibrational energy of the
32
1
*
photodissociation on the n␴ surface. For 157 nm photo-
dissociation, trans-DCE dissociates directly via the Clϩ
˙
CHϭCHCl channel following the photoexcitation to the
1
*
n␴ state.
No HCl elimination was observed for the 157 nm pho-
todissociation of trans-DCE. This result suggests that the
1
*
internal conversion to the ground state from the n␴ state is
a minor process. However, there are two peaks for the trans-
lational energy distribution for reaction ͑2͒ as shown in Fig.
9f. For the 193 nm photodissociations, the slow Cl compo-
nents are produced via the electronic ground state because
the peaks of the translational energy distributions are at zero
as shown in Figs. 9a–9d. On the other hand, for the 157 nm
photodissociation of trans-DCE, the slow peak is not at zero
as shown in Fig. 9f. When the slow peak of the translational
energy distribution is assumed to be at zero, the peak at
ϳ300 ␮s of TOF spectrum ͑Fig. 5c͒ could not be reproduced
and the peak of the simulated curve appears ϳ200 ␮s slower
than that of the measured spectrum. The slow Cl component
is not produced by the dissociation via the electronic ground
state in the 157 nm photodissociation of trans-DCE. This
product. Thus, E is not sensitive to the wavelength of the
͗
͘
t
dissociation laser.
The 3C and 4C eliminations can be competitive5 in the
dissociation from the original geometry of trans-DCE. For
cis-DCE, only the 3C elimination is possible from the origi-
nal geometry;
1
‡
*
CHClϭCHCl͑ ␲␲ ͒→ CHClϭCHCl
→ HClϩ:CϭCHCl
193ϭ317 kJ molϪ1
E
,
where E193 is the total available energy at 193 nm. On the
other hand, only the 4C elimination is possible from the
original geometry of 1,1-DCE:
component will be produced via an excited state other than
1
*
the n␴ state. The internal conversion to the ground state
1
‡
1
*
from the n␴ state is a minor process in the 157 nm pho-
*
CH2ϭCCl2͑ ␲␲ ͒→ CH2ϭCCl2
todissociation of trans-DCE.
→ HClϩCHϵCCl
E
193ϭ494 kJ molϪ1
.
C. HCl elimination
As listed in Table II, the relative yields of HCl at 193 nm
are 0.3, 0.5, 0.5, and 0.2 for cis-DCE, trans-DCE, 1,1-DCE,
and TCE, respectively. The HCl yield for TCE is the small-
est of the four chloroethylenes examined. Moss et al. have
also reported that the relative yield of HCl in the 193 nm
photodissociation of TCE is much smaller than that for
DCE.9 In the UV photodissociation, the HCl elimination is
believed to proceed via the electronic ground state.5,10 The
HCl yield is considered to be mainly controlled by the com-
Since the available energy for the 3C elimination is much
lower than that for the 4C elimination,26,27 the translational
and internal energies of the product for cis-DCE are expected
to be lower than those for 1,1-DCE. However, the mean
translational energies for reaction ͑1͒ obtained at 193 nm are
closest among the three isomers of DCE as listed in Table I.
In addition, the internal energy of HCl for 1,2-DCE is also
nearly the same as that for 1,1-DCE as described by He
et al.13 and Sato et al.14 These results are strange considering
J. Chem. Phys., Vol. 106, No. 24, 22 June 1997
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

10132
Sato et al.: Photodissociations of chloroethylenes
from the different available energies for the 3C and 4C
eliminations. He et al. suggested that the product of the 3C
elimination :CϭCHCl isomerizes to CHϵCCl at around the
transition state region and the product of the 4C elimination
can also be formed via the 3C elimination.13 Sato et al. have
suggested that the 1,1-1,2 and cis-trans isomerizations com-
pete with the HCl elimination.14,15 All previous workers im-
plied that the memory of the original geometry is lost during
elimination because of atom migration processes. If this is
the case, product energies become the same among the three
isomers of DCE for all the degrees of freedom. The present
results give support to these explanations. In order to explain
both the present results of the translational energy and the
previous results of the internal energy, it is desirable to as
sume that the memory of the original geometry is lost during
the elimination.
V. CONCLUSION
We have obtained the translational energy distributions
and the branching ratios of the products in the 193 and 157
nm photodissociations of cis-, trans-, and 1,1-DCE and TCE.
The overall mechanisms for the 193 nm photodissociation
and a part of those for the 157 nm photodissociation have
been elucidated. For the absorption of 193 nm, chloroethyl-
1
*
enes, CHXϭCClY ͑X, YϭH or Cl͒, excited to the ␲␲
1
*
state dissociate either via the n␴ state or via the electronic
ground state as follows:
˙
It has been found that chlorinated vinyl radical, CHXϭCY,
11 P. T. A. Reilly, Y. Xie, and R. J. Gordon, Chem. Phys. Lett. 178, 511
͑1991͒.
produced by the C–Cl bond rupture dissociates spontane-
ously to XϩCHϵCY even in the 193 nm photodissociation
because the vinyl radical is vibrationally excited. C2H2 pro-
duced by the UV photodissociation of 1,2-DCE2,3 and the H
produced by the 193 nm photodissociation of 1,1-DCE20 are
the products of the secondary dissociations of vinyl radicals.
In the 157 nm photodissociation of trans-DCE, DCE mol-
ecules in the n␴ state are initially produced by the absorp-
tion and dissociate directly to ClϩCHϭCHCl. In the 157 nm
photodissociations of cis-, 1,1-DCE, and TCE, chloroethyl-
12 Y. Huang, Y. Yang, G. He, and R. J. Gordon, J. Chem. Phys. 99, 2752
͑1993͒.
13 G. He, Y. Yang, Y. Huang, and R. J. Gordon, J. Phys. Chem. 97, 2186
͑1993͒.
14 K. Sato, Y. Shihira, S. Tsunashima, H. Umemoto, T. Takayanagi, K.
Furukawa, and S. Ohno, J. Chem. Phys. 99, 1703 ͑1993͒.
15 K. Sato, S. Tsunashima, T. Takayanagi, K. Yokoyama, G. Fujisawa, and
A. Yokoyama, Chem. Phys. Lett. 232, 357 ͑1995͒.
16 K. Sato, S. Tsunashima, T. Takayanagi, G. Fujisawa, and A. Yokoyama,
Chem. Phys. Lett. 242, 401 ͑1995͒.
1
*
˙
17 K. Yokoyama, G. Fujisawa, and A. Yokoyama, J. Chem. Phys. 102, 7902
͑1995͒.
1
1
*
enes excited to the ␲3p state dissociate via the ␲␲ state
by the similar mechanism to that of the 193 nm photodisso-
ciation.
18 G. He, Y. Yang, S. Hashimoto, and R. J. Gordon, J. Chem. Phys. 103,
5488 ͑1995͒.
19 M. Umemoto, K. Seki, H. Shinohara, U. Nagashima, N. Nishi, M. Ki-
noshita, and R. Shimada, J. Chem. Phys. 83, 1657 ͑1985͒.
20 Y. Mo, K. Tonokura, Y. Matsumi, M. Kawasaki, T. Sato, T. Arikawa, P.
T. A. Reilly, Y. Xie, Y. Yang, Y. Huang, and R. J. Gordon, J. Chem.
Phys. 97, 4815 ͑1992͒.
ACKNOWLEDGMENTS
K.S. is grateful to Professor Toshinori Suzuki for helpful
suggestions and discussions on the reaction mechanism. K.S.
also wishes to thank Professor Nobuyuki Nishi for helpful
advises to the detection system.
21 T. Suzuki, K. Tonokura, L. S. Bontuyan, and N. Hashimoto, J. Phys.
Chem. 98, 13 447 ͑1994͒.
22 Y. Huang, G. He, Y. Yang, S. Hashimoto, and R. J. Gordon, Chem. Phys.
Lett. 229, 621 ͑1994͒.
23 Y. Huang, Y. Yang, G. He, S. Hashimoto, and R. J. Gordon, J. Chem.
Phys. 103, 5476 ͑1995͒.
24 E. Zamir and R. D. Levine, Chem. Phys. Lett. 67, 237 ͑1979͒.
25 E. Zamir and R. D. Levine, Chem. Phys. 52, 253 ͑1980͒.
26 J. Riehl and K. Morokuma, J. Chem. Phys. 100, 8976 ͑1994͒.
27 J. Riehl, D. G. Musaev, and K. Morokuma, J. Chem. Phys. 101, 5942
͑1994͒.
1 T. Fujimoto, A. M. Rennert, and M. H. J. Wijnen, Ber. Bunsenges. Phys.
Chem. 74, 282 ͑1970͒.
2 R. Ausubel and M. H. J. Wijnen, Int. J. Chem. Kinet. 7, 739 ͑1975͒.
3 R. Ausubel and M. H. J. Wijnen, J. Photochem. 4, 241 ͑1975͒.
4 R. Ausubel and M. H. J. Wijnen, J. Photochem. 5, 233 ͑1976͒.
5 M. J. Berry, J. Chem. Phys. 61, 3114 ͑1974͒.
28 X. Zhao, Ph. D. thesis, University of California, Berkeley, 1988.
29 B. A. Balko, J. Zhang, and Y. T. Lee, J. Chem. Phys. 97, 935 ͑1992͒.
30 S. W. North, C. A. Longfellow, and Y. T. Lee, J. Chem. Phys. 99, 4423
͑1993͒.
6 C. Reiser, F. M. Lussier, C. C. Jensen, and J. I. Steinfeld, J. Am. Chem.
Soc. 101, 350 ͑1979͒.
7 A. S. Sudbø, P. A. Schulz, E. R. Grant, Y. R. Shen, and Y. T. Lee, J.
Chem. Phys. 68, 1306 ͑1978͒.
31 S. W. North, D. A. Blank, J. D. Gezelter, C. A. Longfellow, Y. T. Lee, J.
Chem. Phys. 102, 4447 ͑1995͒.
8 A. S. Sudbø, P. A. Schulz, Y. R. Shen, and Y. T. Lee, J. Chem. Phys. 69,
2312 ͑1978͒.
32 A. Yokoyama, T. Takayanagi, and G. Fujisawa, J. Chem. Phys. 103, 1710
͑1995͒.
9 M. G. Moss, M. D. Ensminger, and J. D. McDonald, J. Chem. Phys. 74,
6631 ͑1981͒.
33 A. Yokoyama, K. Yokoyama, and G. Fujisawa, J. Chem. Phys. 100, 6487
͑1994͒.
10 D. J. Donaldson and S. R. Leone, Chem. Phys. Lett. 132, 240 ͑1986͒.
J. Chem. Phys., Vol. 106, No. 24, 22 June 1997
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32

Sato et al.: Photodissociations of chloroethylenes
34 R. D. Levine and R. B. Bernstein, Molecular Reaction Dynamics and
10133
Interscience, London, 1972͒.
Chemical Reactivity ͑Oxford, New York, 1987͒.
35 A. Yokoyama, A. Yokoyama, and G. Fujisawa, Bull. Chem. Soc. Jpn. 68,
3355 ͑1995͒.
37 G. Poulet, G. Le Bras, and J. Combourleu, J. Phys. Chem. 81, 2303
͑1977͒.
38 S. A. Safron, N. D. Weinstein, D. R. Herschbach, and J. C. Tully, Chem.
Phys. Lett. 12, 564 ͑1972͒.
36 P. J. Robinson and K. A. Holbrook, Unimolecular Reactions ͑Wiley-
J. Chem. Phys., Vol. 106, No. 24, 22 June 1997
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:
136.165.238.131 On: Wed, 24 Dec 2014 05:25:32