NONADIABATIC EFFECTS ON RESONANCE-ENHANCED RAMAN-SCATTERING IN H2

Resonance-enhanced Raman scattering (RERS) from the ground X1SIGMA(g)+(v(g) = 0, J(g)) state Of H-2 via the excited intermediate C1PI(u)(v(iC) = 0/1/2/3, J(i)) state coupled non-adiabatically with the B1SIGMA(u)+(v(iB) = 8/10/12/14, J(i)) state was studied theoretically, applying second-order perturbation theory. The excitation and Raman spectra for the pure rotational, fundamental and higher overtones are presented. Effects of non-adiabatic coupling on the excitation profiles, scattered intensities and depolarization ratios were investigated. Tbe intensities of excitation spectra and Raman lines for O-, Q- and S-branches were calculated using thermal Boltzmann factors for vibrational-rotational distribution at room temperature (300 K). The RERS cross-sections with adiabatic and non-adiabatic corrections are reported together with Born-Oppenheimer (BO) results where available, for comparison. The calculated RERS cross-sections including non-adiabatic effects were found to vary significantly from adiabatic or BO results.