AN INVESTIGATION OF THE SO(X3-SIGMA-) MOLECULE BY MULTIPHOTON IONIZATION SPECTROSCOPY

Rydberg states of the SO molecule, in the region 62 500-67 500 cm-1 above the neutral ground state, have been studied using both (3 + 1) and (2 + 1) resonance enhanced multiphoton ionization (MPI) spectroscopy. Band assignment has been assisted by recording spectra with both linearly and circularly polarized radiation, by simulation of rotational band contours and by calculating quantum defects for the observed Rydberg states. Transitions to four Rydberg states (the 3-DELTA(4p-pi), 3-PI(3d-gamma), 3-PI(3d-sigma) and 3-PHI(3d-gamma) states) have been observed corresponding to promotion of an electron from the outermost occupied pi-molecular orbital in SO(X3-SIGMA-) to the 4p-pi, 3d-gamma and 3d-sigma Rydberg orbitals. For each state, spectroscopic constants have been derived from the experimental spectra. A (2 + 2) MPI spectrum of a known valence state, the B3-SIGMA-, upsilon' = 8 state, has also been obtained.