INTERMOLECULAR VIBRATIONAL ENERGY REDISTRIBUTION IN NAPHTHALENE AND SOME OF ITS SUBSTITUTED DERIVATIVES--OBSERVED IN A FREE JET

Abstract

The rate of intramolecular vibrational energy redistribution following optical excitation has been measured in the absence of collision for naphthalene and some of its substituted derivatives. By using the technique of fluorescence excitation in a free jet, we are able to measure the $S_{1} \leftarrow S_{0}$ absorption linewidths as a function of excess vibrational energy above the origin for an isolated molecule. From these linewidths we extract the rates of vibrational energy redistribution for naphthalene and derivatives. The rate increases with excess vibrational energy, ranging in naphthalene from $9 \times 10^{10} \sec^{-1}$ at $3069 cm^{-1}$ above the $S_{1}$ origin to $9 \times 10^{11} \sec^{-1}$ at $4300 cm^{-1}$ above the $S_{1}$ origin.