15min:

THOMAS MÜLLER, PATRICK DUPRÉ AND PATRICK H. VACCARO, Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06520; FRANCISCO PEREZ-BERNAL AND FRANCESCO IACHELLO, Center for Theoretical Physics, Yale University, New Haven, CT 06520.

An algebraic theory, based upon expansion of the molecular Hamiltonian in terms of bosonic creation and annihilation operators, has been used to extract detailed vibrational information from vibronically-resolved emission spectra of jet-cooled S₂O molecules. The fluorescence accompanying selective excitation of single rovibronic lines in the 2²₀3¹₀ and 2^v_o ( v =0-3) bands of the intense C ¹\!\textrmA' <- X ¹\!\textrmA' (^*\!<- \!) absorption system were dispersed under moderate spectral resolution (5-10 cm^-1). Ground state vibrational levels possessing as much as 20 quanta of excitation in the ₂ S-S stretching mode and residing up to ~13000 cm^-1 above the vibrationless X ¹\!\textrmA' zero-point energy have been observed and assigned.

Detailed analyses of S₂O vibrational energies within the X and C manifolds, as well as their interconnecting vibronic resonances, have been performed through a U (2) based algebraic treatment. Although computationally no more intensive than a Dunham-like expansion, this approach offers the ability to extract multidimensional wavefunctions and related vibrational information. In particular, Franck-Condon factors and vibronic transition amplitudes can be evaluated efficiently without recourse to arduous numerical calculations.

The emerging picture of S₂O vibrational dynamics suggests that the X ¹\!\textrmA' surface is substantially more "local" in nature than the C ¹\!\textrmA' state, with the latter exhibiting significant mixing of vibrational character among the ₁ (S-O stretching), ₂ (S-S stretching) and (to a lesser extent) ₃ (bending) degrees of freedom. Structural parameters deduced from algebraic analyses largely confirm the C ¹\!\textrmA' equilibrium geometry inferred from previous studies under the assumption of an unchanged S-O bond length upon C <- X excitation.