Laser Spectroscopic and Theoretical Studies of Silicon and Germanium-Containing Species.

A detailed examination of both the ground (\tilde{X}¹A´) and first excited (ù A´´) singlet states of HSiNC and HSiNCO have been carried out through analysis of the 520-420 nm and 490-450 nm band systems, respectively. HSiNC and HSiNCO have been generated by electric discharge through (CH_3)_3SiCN and (CH_3)_3SiNCO vapour in argon, respectively. The pulsed electrical discharge jet coupled with laser induced fluorescence (LIF) and dispersed fluorescence (DF) techniques were employed to investigate these species. Previous theoretical and microwave studies were used for comparison with the HSiNC species. Rotational analysis of the 0_0ˆ0 band yielded a new set of rotational constants for both the ground and excited states of both species. Eleven vibrational bands have been tentatively assigned for both species in their excited states. DF spectroscopy has also been applied to both species. As there have been no previous studies on HSiNCO, a detailed ab initio study has been carried out on the possible [H, Si, N, C, O] isomers, with particular attention paid to the HSiNCO species, for use as comparison with the aforementioned experimental study. Different levels of theory have been applied to the seven lowest lying isomers and the transition states connecting them have also been determined. The stability of the isomers has also been checked by carrying out thermodynamic calculations. Finally, as a continuation of the silicon work, a detailed ab initio study has been carried out on the previously unstudied [H, Ge, N, C, O] isomers. Different levels of theory have been applied to the five lowest lying isomers, and their stability has been checked by carrying out thermodynamic calculations