Pseudo-exact force constants from coriolis coupling constants

Abstract

A method has been developed to calculate Pseudo-Exact Force Constants from ζ-constants after truncating a higher dimensional secular equation with the High Low Frequency Separation Method (PE-HFS and PE-LFS method). A procedure to reduce the C-matrix is presented and the conditions for the applicability will be discussed. The present method is applicable to many cases where only one ζ-constant can be measured (e.g., if some band contours are disturbed and prevent the determination of all ζ-values). It is also possible to get excellent starting force constants for a least square programme in cases where sufficient data are known. The effectiveness of the different first order ζ-constants in fixing the force constants has been pointed out. The pseudo ζ sum rule for the truncated secular equation is also discussed. A proof for the sign rule for ζ-constants for xzy 3 ( C 3 v ) type molecules [ζ(δ as (XY 3)) < 0 and ζ(ϱ r (XY 3)) > 0] is given.