Vibronic relaxation among the Clements bands of SO2 from the E-band excitation

Abstract

Vibronic relaxation among the Clements bands of SO2 molecule has been studied from time-resolved fluorescence spectra in the 300-350 nm region. The K' = 6, J' = 7 level of the Clements E-band was populated at 32 812.8 cm(-1), and detailed time-resolved fluorescence spectra for the period 0-160 ns were obtained. Following the fast decay of the laser excited level, weak emissions from Clements A-F bands appeared almost simultaneously. The simultaneous appearance of many Clements bands was attributed to fast rovibronic relaxation of the laser excited molecules among the dark levels. It was also found that the broad apparent continuum emission following the direct fluorescence showed different decay rates at different wavelengths, but the decay rates of the emissions for lambda > 350 nm were virtually identical. Based on the wavelength dependence of the decay rates, the apparent continuum emissions were ascribed to the emissions from the rovibronically dispersed hybrid bright states and the low-lying rovibrational levels of the (A) over tilde(1)A(2) state generated by collisional relaxation of the laser-excited level.