Abstract

The spectra of a number of carbenes, silylenes, and germylenes have been recorded under jet-cooled conditions by pyrolysis of stable precursors in the throat of a supersonic nozzle. The strong S₁–S₀ transitions can be rotationally resolved in some cases, providing detailed information on the ground and excited state molecular structure. In the heavier species, only the vibronic structure is resolvable, yielding ground and excited state vibrational frequencies and band origins. In the case of GeCl₂, we have also been able to obtain a jet-cooled phosphorescence excitation spectrum of the T₁–S₀ transition at 440 nm, providing, to our knowledge, the first direct lase excited detection of the triplet state of any of the carbene or carbene-like species. Ab initio predictions of the excited state energies and vibrational frequencies have been used to provide a consistent picture of the excited states of the germylenes, clearing up a lot of confusion in previous literature assignments. These studies provide the basis for sensitive spectroscopic detection of the carbene analogs, many of which are important in semiconductor growth processes.

© 1992 Optical Society of America