Direct spectroscopic evidence for a new, lowhyphen;lying electronic triplet state in SO2at 4.2 K

摘要

The phosphorescence emission and excitation spectra of crystalline SO2at 4.2 K exhibit an anomalous energy gap of 83 cmminus;1between their respective origins. The phosphorescence excitation, whose sharp origin occurs at 26 387 cmminus;1, involves a transition between the1A1ground state and the excited3B1state. However, our data indicate that the phosphorescence emission originates from a second triplet state, which lies 83 cmminus;1lower in energy. A very weak absorption at 26 304 cmminus;1is observed in the phosphorescence excitation spectrum, which exactly coincides with the observed phosphorescence emission origin. Sitehyphen;selection experiments eliminate the possibility that the observed emission is due to defect sites in the crystal, and confirm the existence of the previously unreported lowhyphen;lying triplet state. Phosphorescence lifetime data and the observed timehyphen;resolved emission spectra are consistent with this finding.