Direct Measurement of the Three-Dimensional Product Velocity Distribution from Photoinitiated Bulb Reactions

Abstract

We describe an apparatus designed to measure the velocity distribution of products of photoinitiated bulb reactions. A photolytic precursor AX and reactant BC are coexpanded into a vacuum chamber. A photolysis laser initiates the reaction sequence AX+hν→A+X, A+BC→AB+C. The C product is detected by sub-Doppler (1+1+1) resonance-enhanced multiphoton ionization (2D-REMPI) to yield its three-dimensional velocity distribution. If this technique were to be applied to the AB(υ',J') product, it would be possible to measure the alignment dependence of the state-to-state differential cross section. We present the experimentally determined velocity distribution of H atoms from the photolysis of HI and D atoms from the reaction H+D 2 →HD+D, and we show that our measurements are consistent with previous studies