PHONON-INDUCED SCATTERING BETWEEN VIBRATIONS AND MULTIPHOTON VIBRATIONAL UP-PUMPING IN LIQUID SOLUTION

Fast phonon-induced scattering between an infrared active and a Raman active vibration in solution is investigated using picosecond infrared pump/anti-Stokes Raman probe experiments. Population from the infrared active T1u CO stretching mode of tungsten hexacarbonyl in carbon tetrachloride at 1980 cm-1 scatters to the Raman active E(g) mode at 2012 cm-1 but not to the A1g mode at 2116 cm-1. Equilibration occurs rapidly compared to the 700 ps population relaxation time. A power dependence of the line shape of the Raman mode indicates that significant population is pumped into high vibrational levels when high infrared pump powers are used.