REANALYSIS OF VIBRATIONAL RESONANCES IN $SiH_{2}\ \tilde{X}\ ^{1}A_{1}$

1. H. Ishikawa and O. Kajimoto, J. Mol. Spectrosc. 150, 610 (1991), ibid. 160, 1 (1993.)Author Institution: Departement of Chemistry, Massachusetts Institute of Technology; Department of Chemistry, Kyoto UniversityWe have reanalysed the vibrational structure of $SiH_{2} \ \widetilde{X} \ {^{1} A_{1}}$. In the previous $study^{1}$, we found the following three groups of $1 \nu_{1}-2\nu_{2}$ Fermi resonances, $(1,0,0)-(0,2,0)-(1,1,0,)-(0,3,0), (2,0,0)-(1,2,0)-(0,4,0)$. In addition, we found a $2 \nu_{1}-2\nu_{3}$ Darling-Dennison (D-D) resonance between the (2,0,0) and (0,0,2) levels. In our previous analysis, the D-D resonance was ignored and 5 vibrational constants, $\omega^{0}_{1}, x_{11}, \omega^{0}_{2}, x_{22}, x_{12}$, and the Fermi interaction energy, $W_{020,100}$ were obtained. One problem was that our value of $X_{11}$ was positive. We considered that the reason for the positive value of $x_{11}$ is our neglect of the D-D resonance. In this study, taking the D-D resonance into account, the following preliminary constants $(cm^{-1})$ were obtained: \[ \begin{array}{l} \omega^{0}_{1}=2004.00, x_{11} = -11.46, \omega^{0}_{2}=1002.19, x_{22}=3.165, x_{12}=-18.04,\\ E^{0}_{002}=3936.69, |W_{020-100}| = 13.456, |W_{D-D}| = 31.61. \end{array} \] This D-D resonance energy between the (2,0,0) and the (0,0,2) levels is comparable to the Fermi resonance energy between the (0,4,0) and (1,2,0) levels. It was confirmed that the previous positive value of $x_{11}$ was due to the neglect of the D-D resonance. Details of the analysis will be presented