FLUORESCENCE OF INDIRECTLY EXCITED LOW VIBRATIONAL LEVELS OF THE (1)A(2) STATE OF SULFUR-DIOXIDE

Vibronic levels of the (1)A(2) State of SO2 were excited by crossing a supersonic jet of SO2 with laser radiation corresponding to cold band s in the 3045-3005 Angstrom region, and the emission spectrum was dete cted under different laser-jet geometrical alignments. When the exciti ng laser beam was allowed to cross the jet just outside the spectromet er's field of view, a vibrational fluorescence spectrum of simultaneou sly excited low 1A, levels was measured and was found to be independen t of the exciting wavelength. This indicated that these levels were po pulated through inelastic collisions within the jet and that the low-l ying (1)A(2) levels do in general fluoresce back to the ground state. Fourteen band origins near the (1)A(2)(0,0,0)' --> (1)A(2)(0,0,0)'' tr ansition at 3581 Angstrom were thus identified to within +/-1 Angstrom . An excitation spectrum recorded while monitoring the fluorescence of these collision-populated low (1)A(2) levels showed many cold bands t hat have not been detected before and also showed that the efficiency of energy transfer due to collisions depended on the initially excited vibronic level.