Knowledge Bank

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 $\nu 2,\nu 3,\nu 4$, and $\nu 6$ 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.