The detection and characterization of silicon- and germanium-containing radicals using laser based spectroscopic methods

The A&d15;S+ 2-X&d15;Pi 2 transition of jet-cooled silicon methylidyne, SiCH, and germanium methylidyne, GeCH, have been recorded by laser-induced fluorescence (LIF) in the 850--555 nm region. The SiCH and GeCH radicals were produced in an electric discharge using tetramethylsilane and tetramethylgermane as the precursors, respectively. Vibrational analysis of low-resolution spectra allowed for the determination of the upper state vibrational frequencies as n'2 (SiCH/GeCH) bend and n'3 (CSi/CGe) stretching. The analysis of rotationally resolved high-resolution spectra for each isotopomer (SiCH/SiCD) and (GeCH/GeCD) allowed for their molecular structures to be determined for both the ground and excited electronic states. The silicon-carbon and germanium-carbon bond length in the A&d15;S+ excited state corresponds to a triple bond. This work provides the first experimental measurement of the length of the carbon-silicon and carbon-germanium triple bond.;The ground state vibrational energy levels of jet-cooled SiCH, GeH 2 and H2CSi have been studied by a combination of laser-induced fluorescence and wavelength-resolved fluorescence techniques. The radicals were produced by a pulsed electric discharge at the exit of a supersonic expansion. Emission spectra have been obtained by pumping strong vibronic bands from the LIF spectra, providing complementary information on the ground state vibrational modes. Beyond low-resolution emission spectra, high-resolution stimulated emission pumping (SEP) spectra of H2CSi were recorded to give precise measurements of the vibrational band origins of many of the lower-lying vibrational levels. The A&d15;S+ 2-X&d15;Pi 2 emission spectra of SiCH were used to study the Renner-Teller effect in the X&d15;Pi 2 ground state where the vibrational levels were complicated due to the interaction between vibrational and electronic motion. The validity of the derived parameters has been tested using the deuterium isotope relations for each of the corresponding radicals.