15min:

SHENG-GUI HE AND DENNIS J. CLOUTHIER, Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055.

The A ¹A₂ states of H₂CGe and D₂CGe have been explored for the first time by A - X laser-induced fluorescence (LIF) spectroscopy of the orbitally forbidden S₁ - S₀ transition and stimulated emission pumping (SEP) and wavelength resolved fluorescence studies of the allowed B - A electronic transition. Medium-resolution SEP studies gave the excited A state ₂, ₃, ₄, and ₆ vibrational frequencies for H₂C⁷⁴Ge and D₂C⁷⁴Ge. The 4¹ and 6¹ levels and higher combination and overtone states are strongly Coriolis coupled, which perturbs the rotational subband structure, limiting the accuracy of the determination of the vibrational frequencies. High-resolution SEP studies of the B - A 0₀⁰ band have allowed us to determine the rotational constants of the A state of H₂C⁷⁴Ge, from which we were able to calculate an approximate r₀ structure with the CH bond length constrained to the ground state value. The zero-point level of D₂C⁷⁴Ge is substantially perturbed, most plausibly by interaction with an excited vibrational level of the nearby triplet (a ³A₂) state.