Recombination and relaxation dynamics of diatomic molecules in condensed phases

Abstract

Picosecond absorption kinetics of I2 and Br2 in room temperature CCl4 are presented. Several probe wavelengths were used following excitation with 30ps pulses of 532nm light. The results indicate that population of the electronically excited A(3πlu) and A’(3π2u) states occur rapidly (<30ps) following dissociation. Analysis of transient absorption intensities indicates that repopulation of the ground electronic state of I2 requires about 30–50ps. The difference in population times may be understood in terms of trapping in weakly bound electronic states (perhaps 3π0–u) which relax to populate the ground state, or in terms of slow atom recombination into the ground state. Vibrational relaxation rates through the ground state manifoeld were interpreted in terms of vibration to translation energy transfer as given by the Schwartz, Slawsky, Herzfeld theory.