Vacuum ultraviolet absorption spectra of thiirane and thietane

Abstract

Photoabsorption cross sections of thiirane and thietane vapors have been studied in the 110–240 nm region using synchrotron radiation. A number of peaks from thiirane and thietane are arranged into four and five Rydberg series, respectively, converging to the first ionization potential. Many Rydberg peaks from both molecules are observed to possess vibronic structures. The vibrational progressions from thiirane are assigned to the CH2 wagging (ν4) and CS symmetry stretching (ν5) modes. For thietane, the CH2 wagging (ν5) and CS symmetry stretching (ν7) modes of the excited states are found to be active. Molecular geometries and vibrational frequencies for the excited states are discussed on the basis of ab initio calculations.