Ultrafast transient Raman investigation of geminate recombination and vibrational energy relaxation in iodine: The role of energy relaxation pathways to solvent vibrations

Abstract

Direct observation of geminate recombination and vibrational energy relaxation in the X state of iodine has been accomplished using picosecond Raman spectroscopy. The dynamics of energy relaxation from vibrational levels ranging from v=52 to v=1 have been observed. These levels correspond to absolute energies of 9300 to 210 cm−1 above the zero point in the X potential. The effect of relaxation to solvent vibrations in resonance with I2 vibrations has been studied. The efficiency of these vibrational–vibrational relaxation channels is found to be very solvent dependent. The results suggest that the vibrational coupling between the excited iodine oscillator and the solvent is drastically affected by the nature of the normal mode character of the solvent vibration.