ZERO-ORDER B-1(1)(N,O,O) VIBRATIONAL LEVELS OF SULFUR-DIOXIDE

More than 100 single vibronic level fluorescence spectra of SO2 throug hout the 30 400-34 230 cm(-1) spectral region were selectively excited and recorded in crossed supersonic jet and laser beams under conditio ns of cold rotational temperatures. It was found that the vibronic ori gins can be grouped into 5 overlapping regions based on identical Fran ck-Condon patterns of the (X) over tilde A(1)(n,0,0) progressions. The spacing between the centers of these regions was found to range betwe en 572 cm(-1) and 647 cm(-1) as opposed to the previously estimated va lue of 690 cm(-1). The onset of the B-1(1) state in the vibronic coupl ing was found to be at the 30 553 cm(-1) band, which is below the prev iously reported threshold energy by 220 cm(-1). The results provide qu alitative verification of the multilevel coupling mechanism proposed b y Kullmer and Demtroder [Chem. Phys. 92, 323 (1985)]. (C) 1998 America n Institute of Physics. [S0021-9606(98)01533-5].