Rotational effects on intramolecular vibrational relaxation in dimethyl ether and 1,4 dioxane

Abstract

The effect of rotational excitation on intramolecular vibrational relaxation in isolated gas phase molecules of dimethyl ether and 1,4 dioxane has been studied. Frequency resolved infrared fluorescence spectra were obtained from molecules isolated in a supersonic expansion and excited in the CH stretching region with an infrared optical parametric oscillator. By altering the expansion conditions the average J of the molecules was controlled. Measurements performed on both molecules at two different rotational temperatures indicate that the dilution factors of the CH stretch modes have a significant J dependence. It is demonstrated that the measured energy contents of the relaxed modes can be satisfactorily modeled by a statistical calculation which assumes equal coupling of all modes with 1 cm-1 of the optical state which conserve J and symmetry. It is shown that the ultimate distribution of the energy within the molecule is J dependent. © 1986 American Institute of Physics.