The ground state of silylidene (H[sub 2]C=Si), the silicon analog of vinylidene, from stimulated emission pumping and wavelength-resolved fluorescence spectroscopy.

The ground state vibrational energy levels of jet-cooled H[sub 2]CSi and D[sub 2]CSi have been studied by a combination of wavelength-resolved fluorescence and stimulated emission pumping (SEP) techniques. By taking advantage of the vibrational selection rules and Franck-Condon factors and selectively pumping upper state single vibronic levels, readily assignable low-resolution emission spectra were obtained. Higher resolution SEP spectra were recorded to give precise measurements of the vibrational band origins of many of the lower-lying vibrational levels. All of the vibrational frequencies, except for the Franck-Condon inactive CH asymmetric stretching mode, ν[sub 5], have been determined for both isotopomers. The CH[sub 2] rocking mode (ν[sub 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. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]