A stimulated emission pumping study of the first excited singlet state of germylidene (H2C=Ge)

The A (1)A(2) states of H(2)CGe and D(2)CGe have been explored for the first time by A-X laser-induced fluorescence (LIF) spectroscopy of the orbitally forbidden S(1)-S(0) 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 nu(2), nu(3), nu(4), and nu(6) vibrational frequencies for H(2)C(74)Ge and D(2)C(74)Ge. The 4(1) and 6(1) 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 0(0) (0) band have allowed us to determine the rotational constants of the A state of H(2)C(74)Ge, from which we were able to calculate an approximate r(0) structure with the CH bond length constrained to the ground state value. The zero-point level of D(2)C(74)Ge is substantially perturbed, most plausibly by interaction with an excited vibrational level of the nearby triplet (a (3)A(2)) state.