Knowledge Bank

$SiH2$ is one of the simplest silicon containing radicals. Similarity and dissimilarity to $CH2$ radical are very interesting from both chemical and spectroscopic points of view. Renner-Teller interaction between the $A~1B1$ and the $X~1A1$ states and an energy separation between the $X~1A1$ and the $a~3B1$ states are very important issues in spectroscopy. An analysis of highly excited vibrational levels in the $X~$ state should provide some valuable information about them. Thus, we have carried out stimulated emission pumping (SEP) spectroscopy on $SiH2$. In the present study, a pulsed discharge nozzle was used to generate jet-cooled $SiH2$ radical. Precursor of $SiH2$ radical was phenylsilane. The $000$ rotational levels of the $A~(060)$ and (070) levels were used as intermediate levels in the present SEP spectroscopy. Until now, vibrational levels with $v2$ up to $4(Evib\le 4000cm-1)$ have been $observeda$. In the present study, 22 vibrational levels in the energy region of $4800-8000cm-1$ were observed. Due to strong $2\nu 2:1\nu 1$ Fermi and $2\nu 1:2\nu 3$ Darling-Dennison resonances, vibrational levels having the same polyad quantum number, $P=2v1+v2+2v3$, construct polyad structures. The vibrational levels observed belong to polyads of $P=5-8$. Taking these resonance into account, vibrational analysis of the $SiH2$ radical was carried out. In the present analysis, vibrational constants, $x13$ and $x23$, could be determined experimentally, for the first time. Preliminary values are $-74.83cm-1$ and $-17.58cm-1$, respectively. Details of the vibrational analysis will be discussed at the presentation.