文摘
Photodissociation dynamics of 2-bromopropane in the A band was investigated at several wavelengths between 232 and 267 nm using resonance-enhanced multiphoton ionization technique combined with velocity map ion-imaging detection. The ion images of Br (2P3/2) and Br* (2P1/2) were analyzed to yield corresponding total translational energy and angular distributions. The total translational energy distributions showed that the channel leading to Br carried more internal energy in the 2-C3H7 moiety than the channel leading to Br*. The anisotropy parameters of β (Br) were obtained to be between 0.68 and 1.49, and β (Br*) between 0.73 and 1.96, indicating that the Br* product originates from direct excitation of the 3Q0 state and the 1Q1 → 3Q0 nonadiabatic transition, and the Br product from direct excitation of the 1Q1 or 3Q1 state and the 3Q0 → 1Q1 nonadiabatic transition. The curve crossing probabilities were determined to be increase with the wavelength. As compared with the case of CH3Br, the two heavier branched CH3 groups significantly enhance the Br (2P3/2) production from nonadiabatic contribution. The curve crossing from the 3Q0 to the 1Q1 surface is much higher than that of the reverse from the 1Q1 to the 3Q0 surface, which may have resulted from the difference in shape between the potential energy surfaces of the 3Q0 and 1Q1 states. Finally, based on the experimental data, the partial absorption cross sections of the A band for the 3Q0, 3Q1, and 1Q1 states were extracted.