Photodissociation of 1,2-C2H2Br2 at 248 nm: Competition between three-bodyformation Br+Br+C2H2 and molecular Br-2 elimination

Citation
Yr. Lee et al., Photodissociation of 1,2-C2H2Br2 at 248 nm: Competition between three-bodyformation Br+Br+C2H2 and molecular Br-2 elimination, J CHEM PHYS, 115(7), 2001, pp. 3195-3200
Citations number
33
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF CHEMICAL PHYSICS
ISSN journal
00219606 → ACNP
Volume
115
Issue
7
Year of publication
2001
Pages
3195 - 3200
Database
ISI
SICI code
0021-9606(20010815)115:7<3195:PO1A2N>2.0.ZU;2-O
Abstract
The photodissociation of 1,2-C2H2Br2 at 248 nm has been studied by product translational spectroscopy. The results show that the molecule dissociates exclusively into the products (1) Br-2+C2H2 and (2) Br (fast)+Br (slow)+C2H 2 with a branching ratio similar to0.2:0.8. While the cleavages of the C-Br bonds are not symmetric, producing the Br atoms at unequal velocities, the anisotropy of the products indicates that both reactions occur in a fracti on of a rotational period. Following an asynchronous concerted reaction, th e triple products were simulated with the P(E-t) distributions coupled by a symmetric angular distributions. A mechanism consistent with the measured r esults is proposed that the Br-2 elimination is a result of a fast intersys tem crossing from the pi pi* pumped state while the triple products occur v ia a simultaneous asymmetric scission of the C-Br bonds along the n sigma* state. (C) 2001 American Institute of Physics.