Intramolecular vibrational redistribution of CH2I2 dissolved in supercritical Xe

Intramolecular vibrational energy redistribution (IVR) of CH2I2 in supercritical Xe has been studied. The first overtone of the C–H stretching mode was excited with a near infrared laser pulse and the transient UV absorption near 390 nm was monitored. Signals showed a rise and decay profile, which gave the IVR and VET (intermolecular vibrational energy transfer) rates, respectively. Solvent density dependence of each rate was obtained by tuning the pressure at a constant temperature. The IVR rate in supercritical Xe increased with increasing solvent density and asymptotically reached a limiting value. This result suggests that the IVR process of CH2I2 in condensed phase is a solvent-assisted process.