Raman pump/probe measurements of state-to-state energy transfer rates in the v=1 state of H2

Abstract

We have measured state-resolved rotational energy transfer rates of H 2 (v = 1) in collisions with H2 (v = 0) at 295 K, using optical pump/probe techniques. A single rotational level was populated using stimulated Raman pumping, and the degree of collision-induced population transfer was monitored using either coherent anti-Stokes Raman spectroscopy (CARS) or resonance-enhanced multiphoton ionization spectroscopy (REMPI). The CARS and REMPI results are in good agreement; averages of the two sets of rates are 180 ± 27X106 s-1 amagat-1 for j = 0→2 and 50±8X106 s-1 amagat-1 for j = 1 → 3. We also observed transfer of vibrational excitation from paraspin v = 1 states to ortho v = 0 states due to v-v exchange, measuring a rate of 1.9±0.8X106 s-1 amagat-1 for this process. © 1988 American Institute of Physics.