The spectrum of matrix isolated SeO 2: Evidence for slow internal conversion between excited states

Abstract

The spectrum of matrix-isolated SeO 2 was studied between 2200 and 6000 Å at 20°K. A strong absorption with a Franck-Condon maximum near 2750 Å and an origin near 31 000 cm −1 is assigned to the S 3 ← S 0 transition. It coincides with the B ← X system of the gas phase. Weak and broad absorption bands in the 3000–4500 Å region belong to S 1 ← S 0 and possibly also to T 1 ← S 0, corresponding to the gas-phase system C ← X. A strong yellow emission, which has a lifetime of < 0.2 msec in xenon, 2.5 msec in SF 6 and 2.0 msec in C 4F 8, and which consists of a well resolved progression of vibrational bands, is assigned to the transition T 1 → S 0, corresponding to a ̃ 3B 1 → X 1A 1 of SO 2. This yellow phosphorescence is excited in the S 1 ← S 0 region at 3100–3700 Å. Excitation below 3200 Å and with X-rays stimulates a broad blue fluorescence between 3000–4200 Å which we assign to the transition S 3 → S 0. The unusually slow internal conversion, S 3 → S 1 can be attributed to strong perturbation of S 1 by T 1.