VUV photoabsorption spectroscopy of sulphur dioxide in the 1400-1600 ? region: Vibronic analysis of the ?-X system

摘要

Gas phase photoabsorption studies of sulphur dioxide are carried out in the vacuum ultraviolet region using synchrotron radiation. Vibronic Analysis of the ?-X? system lying in the region 1400-1600? is reported for the first time. A larger number of spectral features are resolved compared to earlier reports. While most of the observed bands can be arranged into four series with successive band spacing of 500-620cm ~(-1) in agreement with previous work, we observe two additional series with average separation of ~1750 and ~1000cm ~(-1). Results of the ab initio calculations suggest that at least three dominant excitations are involved in the ?-X? system viz. X?A11→3A11, X?A11→2A21 and X?A11→2B11. The observed vibrational features are found to be mainly due to excitation of the combination modes (ν _1+ν _2) and (ν _2+ν _3) with some contributions from ν _1 and ν _3. Details of the experiment and analysis are discussed in this paper.