Second Differences of Moments of Inertia in Structural Calculations: Application to Methyl-Fluorosilane Molecules

Abstract

An extension and application of the method recently proposed by Pierce for the location of ``near‐axis atoms'' from spectroscopically determined moments of inertia is made. Equations are derived which are required for the application of the method to asymmetric top molecules with C_s symmetry. The method is applied to the determination of silicon coordinates in the molecules CH₃SiH₂F and CH₃SiHF₂. The experimental results are combined with results of previous microwave investigations of these molecules in order to determine their structures. Addition of each fluorine atom lowers the SiC distance. The SiF distance is lowered on adding the second fluorine. In the case of CH₃SiHF₂ the equilibrium conformation (staggered) is also determined.