A COMPARATIVE HIGH-RESOLUTION STUDY OF PREDISSOCIATION LINEWIDTHS IN THE SCHUMANN-RUNGE BANDS OF O-2

Results are presented of a comparative study in which three distinct h igh-resolution experimental techniques (vacuum-ultraviolet laser spect roscopy, laser-induced fluorescence spectroscopy and vacuum-ultraviole t Fourier-transform spectroscopy) were used to study predissociation i n the Schumann-Runge bands of O-2 B (3)Sigma(u)(-)(upsilon')<--X (3)Si gma(g)(-)(upsilon '') with upsilon' = 13 and 14. Our measurements are the first to be performed at high resolution for these levels and repr esent a significant advance on previous knowledge, characterizing comp letely the fine-structure and rotation dependencies of the B (3)Sigma( u)(-)(upsilon = 13 and 14)-state predissociation for the first time. T he measured fine-structure-specific linewidths will result in signific ant improvements in the parameterization of models describing predisso ciation of the B-state and will have an impact on the development of r ealistic photochemical models of the terrestrial atmosphere. Good agre ement was found between linewidths measured using vacuum-ultraviolet l aser spectroscopy and laser-induced fluorescence spectroscopy, but une xpected difficulties arose in determining quantitative linewidths usin g vacuum-ultraviolet Fourier-transform spectroscopy. For each experime ntal technique, the instrumental resolution had to be carefully contro lled and monitored in order to ensure reliable interpretation of the m easured spectra. (C) 1998 American Institute of Physics. [S0021-9606(9 8)00734-X].