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 mul-tiphoton 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 dis-tributions 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 ³Q₀, ³Q₁, and ¹Q₁ states to the products (Br and Br*) were discussed. Relative quantum yield of 0.924 for Br(²P_3/2) at about 234 nm in the photodissociation of 2-bromobutane is derived.