INFRARED VIBRATIONAL INTENSITIES, POLAR TENSORS, AND CORE ELECTRON ENERGIES OF THE GROUP-IV HYDRIDES AND THE FLUOROSILANES

Principal component analysis is used to compare polar tensors of CH4, SiH4, GeH4, and SnH4 and their completely deuterated analogues determi ned from infrared fundamental gas-phase intensities measured in differ ent laboratories. This analysis also includes theoretical polar tenser values obtained from effective core potential universal basis set cal culations as well as from MP2/6-311++G(3d,3p) functions for CH4, SiH4, and SiF4. Theoretical values are also used to resolve sign ambiguitie s in the dipole moment derivatives of SiF4. Preferred polar tenser val ues are proposed for all these molecules. Mean dipole moment derivativ es for SiH4 and SiF4 are related to the 2p core ionization energies us ing the simple potential model proposed by Siegbahn and collaborators. These results are confirmed by MP2/6-311++G(3d,3p) calculations for t hese molecules and for SiH3F, SiH2F2, and SiHF3. This study is extende d to the fluorogermanes using experimental 3p and 3d core electron ion ization energies and mean dipole moment derivatives calculated from MP 2/A-VDZ/6-311++G(3d,3p) wave functions. The simple potential model int erpretation of mean dipole moment derivatives as atomic charges implie s that the silicon charge, +/-0.904e, is slightly higher than the germ anium charge of +/-0.862e.