Photodissociation/photoionization processes of chlorobromomethane induced by femtosecond laser pulses with pump-probe scheme

The photodissociation/photoionization processes of chlorobromomethane (CH2BrCl) induced by femtosecond 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 CH2BrCl in the A-band is in the 100 fs. The decaying tendencies of the fragment ions (CH2Cl+ and CH2Br+) and the parent ion (CH2BrCl+) 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 CH2Cl+ and CH2Br+ are obtained from the relative ratio of the ion intensity and are about 71.6% and 14.2%, respectively.