Vibrational Frequencies from Microwave Data: Semirigid Bender Prediction of the ν11 Bending Fundamental of HC5N

Abstract

A suitably extended version of the semirigid bender Hamiltonian of Bunker and Landsberg (J. Mol. Spectrosc.34, 59-7 5 (1983)) is applied to the available microwave data for HC5N, including satellite transitions involving the low frequency ν11 bending vibration. The resulting nonlinear least-squares fitting of the semirigid bender Hamiltonian allows a prediction for the ν11 vibrational energy. The result of fitting two models for this vibration is that the νl11: 11 ← 00 transition is predicted to lie at approximately 102 cm−1. This is significantly higher than previous predictions of about 75 cm−1. Experience with other molecules suggests that the current prediction should be within about 10% of the actual vibrational frequency.