Photodissociation of 2-Bromobutane by Ion-velocity Map Imaging Technique

The photodissociation dynamics of 2-bromobutane has been investigated at 233.62 and 233.95 nm by ion-velocity map imaging technique coupled with resonance-enhanced multiphoton ionization. The speed and angular distribution of Br and Br* fragments were determined from the map images. The two Gaussian components, shown in the speed distributions of Br and Br* atoms, are suggested to attribute to the two independent reaction paths of photodissociation for 2-bromobutane at 233.62 and 233.95 nm. The high-energy component is related to the prompt dissociation along the C Br stretching mode, and the low-energy component to the dissociation from the repulsive mode with bending and C Br stretching combination. The contributions of the excited (3)Q(0), (3)Q(1), and (1)Q(1) states to the products (Br and Br*) were discussed. Relative quantum yield of 0.924 for Br((2)P(3/2)) at about 234 nm in the photodissociation of 2-bromobutane is derived.