Photodissociation of cis-, trans-, and 1,1-dichloroethylene in the ultraviolet range: Characterization of Cl(2Pj) Elimination
Journal
Journal of Physical Chemistry A
Journal Volume
114
Journal Issue
1
Pages
37-44
Date Issued
2010
Author(s)
Hua, L.
Zhang, X.
Lee, W.-B.
Chao, M.-H.
Zhang, B.
KING-CHUEN LIN
Abstract
By using photofragment velocity imaging detection coupled with a (2+1) resonance-enhanced multiphoton ionization technique, the elimination channel of spin-orbit chlorine atoms in photodissociation of cis-, trans-, and 1,1-dichloroethylene at two photolysis wavelengths of 214.5 and 235 nm is investigated. Translational energy and angular distributions of Cl(2Pj) fragmentation are acquired. The Cl(2Pj) fragments are produced by two competing channels. The fast dissociation component with higher translational energy is characterized by a Gaussian distribution, resulting from a curve crossing of the initially excited (π, π*) state to nearby repulsive (π, oσ*) and/or (n, oσ*). In contrast, the slow component with a lower translational energy is characterized by a Boltzmann distribution, which dissociates on the vibrationally hot ground state relaxed from the (π, π*) state via internal conversion. cis-C 2HC2ClC2 is found to have a larger branching of Boltzmann component than the other two isomers. The fraction of available energy partitioning into translation increases along the trend of cis- < trans- < 1,1-CC2HC2ClC2. This trend may be fitted by a rigid radical model and interpreted by means of a torque generated during the C-Cl bond cleavage. The anisotropy parameters are determined, and the transition dipole moments are expected to be essentially along the C=C bond axis. The results are also predicted theoretically. The relative quantum yields of Cl(2PCj) have a similar value for the three isomers at the two photolysis wavelengths.© 2010 American Chemical Society.
SDGs
Type
journal article