A photodissociation study of CH2BrCl in the A-band using the time-sliced ion velocity imaging method

作者：Zhou JG; Lau KC; Hassanein E; Xu HF; Tian SX; Jones B; Ng CY^*

来源：Journal of Chemical Physics, 2006, 124(3): 034309.

DOI：10.1063/1.2158999

Employing a high-resolution (velocity resolution Delta nu/nu < 1.5%) time-sliced ion velocity imaging apparatus, we have examined the photodissociation of CH2BrCl in the photon energy range of 448.6-618.5 kJ/mol (193.3-266.6 nm). Precise translational and angular distributions for the dominant Br(P-2(3/2)) and Br(P-2(1/2)) channels have been determined from the ion images observed for Br(P-2(3/2)) and Br(P-2(1/2)). In confirmation with the previous studies, the kinetic-energy distributions for the Br(P-2(1/2)) channel are found to fit well with one Gaussian function, whereas the kinetic- energy distributions for the Br(P-2(3/2)) channel exhibit bimodal structures and can be decomposed into a slow and a fast Gaussian component. The observed kinetic-energy distributions are consistent with the conclusion that the formation of the Br(P-2(3/2)) and Br(P-2(1/2)) channels takes place on a repulsive potential-energy surface, resulting in a significant fraction (0.40-0.47) of available energy to appear as translational energy for the photofragments. On the basis of the detailed kinetic-energy distributions and anisotropy parameters obtained in the present study, together with the specific features and relative absorption cross sections of the excited 2A(';), 1A(';), 3A(';), 4A(';), and 2A(';) states estimated in previous studies, we have rationalized the dissociation pathways of CH2BrCl in the A-band, leading to the formation of the Br(P-2(3/2)) and Br(P-2(1/2)) channels. The analysis of the ion images observed at 235 nm for Cl(P-2(3/2,1/2)) provides strong evidence that the formation of Cl mainly arises from the secondary photodissociation process CH2Cl+h nu -> CH2+Cl.

• 出版日期2006-1-21