The photodissociation of Br2 was investigated within the near-visible UV absorption band. Based on the potential curves for the ground and low-lying excited states, the optical cross-sections for the discrete transitions of C1^Пu,B^3Пou^＋, A^3П1u←X^1∑g＋ and their total energy absorption spectrum are derived, and the quantum yield of （Br＋Br6＊） channel are determined correspondingly. The one-dimensional Landau-Zener model is used to evaluate the behavior of curve crossing during photodissociation. The results indicate that the influence of nonadiabatic mechanism, which may be caused by the electronic-vibrational interplay between the 13 and C states, is negligibly small for the （Br＋Br^＊） channel. From the Landau-Zener modeling of the observed product recoil parameter β（Br＋Br）, the best-fit value of the coupling matrix elenment or coupling strength between the diabatic B and C state potentials is obtained.
The photodissociation/photoionization processes of chlorobromomethane (CH_2BrCl) induced by fem- tosecond laser pulses have been investigated using pump-probe scheme combined with the time-of-flight mass spectra. The dominate photoproducts are observed at different delay time of the pump (400 nm) and probe (800 nm) pulses and the corresponding time-dependence of them is obtained. The results show that the decaying time of the molecule CH_2BrCl in the A-band is in the 100 fs. The decaying tendencies of the fragment ions (CH_2Cl^+ and CH_2Br^+) and the parent ion (CH_2BrCl^+) are almost the same and the relative ratios of the yields of them keep constant during the delay time of 0 to 150 fs. These facts suggest that the fragment ions come from the fragmentation of the parent ions in excited electronic states. The probabilities to form CH_2Cl^+ and CH_2Br^+ are obtained from the relative ratio of the ion intensity and are about 71.6% and 14.2%, respectively.
ZHANG Feng1,2, WEI ZhengRong1,2, CAO ZhenZhou1,2, ZHANG ChangHua1,2 & ZHANG Bing1,2 1 State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
