The ground state of silylidene (H2C=Si), the silicon analog of vinylidene,from stimulated emission pumping and wavelength-resolved fluorescence spectroscopy

The ground state vibrational energy levels of jet-cooled H2CSi and D2CSi ha ve been studied by a combination of wavelength-resolved fluorescence and st imulated emission pumping (SEP) techniques. By taking advantage of the vibr ational selection rules and Franck-Condon factors and selectively pumping u pper state single vibronic levels, readily assignable low-resolution emissi on spectra were obtained. Higher resolution SEP spectra were recorded to gi ve precise measurements of the vibrational band origins of many of the lowe r-lying vibrational levels. All of the vibrational frequencies, except for the Franck-Condon inactive CH asymmetric stretching mode, nu (5), have been determined for both isotopomers. The CH2 rocking mode (nu (6)) is found to have a very low 263 cm(-1) frequency in the ground state. The spectra are complicated by unexpected activity in the out-of-plane bending vibration. ( C) 2001 American Institute of Physics.