Abstract

Sulfur vapor at high temperatures and low pressures should contain mostly S₂. The absorption and fluorescence spectra of S₂ have been measured extensively over the past century, usually at temperatures well above 600°C. In this study we were interested in the fluorescence spectra at temperatures between 600 and 700°C, where there is a small amount of S₃ present according to thermodynamic predictions. The time-integrated fluorescence spectra in this temperature range show the expected vibrational progression for S₂ with some very weak extraneous features. The temporal decay curves exhibit double-exponential behavior, indicating the presence of two fluorescing components. The ratio of the amplitudes of these two components changes with temperature and pressure similar to the S₂/S₃ concentraton ratio predicted by the thermodyanamic model. We were able to separate the spectral contributions from each of the components by using time-resolved fluorescence spectroscopy. The short-time spectra match the vibrational progression expected from S₂. At longer times, the S₂ contribution vanishes and a much weaker vibrational progression is observable. The spacing in this progression matches well with one of the vibrational mode spacings for S₃.

© 1992 Optical Society of America