Infrared Vibrational Intensities, Polar Tensors, and Core Electron Energies of the Group IV Hydrides and the Fluorosilanes

Abstract

Principal component analysis is used to compare polar tensors of CH4, SiH4, GeH4, and SnH4 and their completely deuterated analogues determined from infrared fundamental gas-phase intensities measured in different laboratories. This analysis also includes theoretical polar tensor values obtained from effective core potential universal basis set calculations as well as from MP2/6-311++G(3d,3p) functions for CH4, SiH4, and SiF4. Theoretical values are also used to resolve sign ambiguities in the dipole moment derivatives of SiF4. Preferred polar tensor values are proposed for all these molecules. Mean dipole moment derivatives for SiH4 and SiF4 are related to the 2p core ionization energies using the simple potential model proposed by Siegbahn and collaborators. These results are confirmed by MP2/6-311++G(3d,3p) calculations for these molecules and for SiH3F, SiH2F2, and SiHF3. This study is extended to the fluorogermanes using experimental 3p and 3d core electron ionization energies and mean dipole moment derivatives calculated from MP2/A-VDZ/6-311++G(3d,3p) wave functions. The simple potential model interpretation of mean dipole moment derivatives as atomic charges implies that the silicon charge, ±0.904e, is slightly higher than the germanium charge of ±0.862e.