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

We have measured state-resolved rotational energy transfer rates of H2 (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 +- 27 x 106 s-1 amagat-1 for j = 0→2 and 50 +- 8 x 106 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 +- 0.8 x 106 s-1 amagat-1 for this process