Knowledge Bank

Analysis of the low-frequency infrared and Raman spectra of 1,3-disilacyclobutane and its $d4$ derivative previously demonstrated that the ring-puckering vibration for this nonplanar molecule was coupled to the $SiH2$ in-phase rocking $motion.1$ Since the $SiH2$ rock and ring deformation modes both give rise to combination band sequences with the ring-puckering, it is possible to determine the ring-puckering energy levels for the excited states of these vibrations. Such data is useful for investigating the interaction of the ring-puckering with the other modes. We have developed a computer program to calculate the vibrational energy levels for a three-dimensional potential energy function. This has, therefore, enabled us to evaluate the effect of the nearly harmonic $SiH2$ rock and ring deformation vibrations on the highly anharmonic ring-puckering mode. The three-dimensional provided a satisfactory representation for these three low-frequency vibrations and resulted in an excellant correlation between experiemental and theoretical values.