Knowledge Bank

Absorption spectra in the $12000cm-1$ to $18000cm-1$ range have been recorded for gaseous $SiHCl3$ and $SiH2Cl2$ using intracavity photoacoustic detection and CW dye lasers. The observed transitions correspond to the $\Delta$V = 6,7,8 and 9 overtones of the Si-H stretch and are adequately interpreted in terms of a local mode description of the vibration. Anharmonic constants of $35.0cm-1$ for $SiHCl3$ and $34.4cm-1$ for $SiH2Cl2$ art found from a Birg-Sponer plot of the higher overtones. The band shape structures are consistence with parallel bands for $SiH2Cl3$ and a B/C hybrid for $SiH2Cl2$.