The spectroscopy and molecular dynamics of the high frequency ν16 intermolecular vibrations in HCN---HF and DCN---DF

Abstract

Gas phase rovibrational analysis of the high frequency intermolecular hydrogen bonded bending overtone 2ν06 [ν0=1132.4783(2) cm−1] in HCN---HF and its corresponding perdeuterated fundamental ν16 [ν0=409.1660(2) cm−1] are reported. Evaluated rovibrational parameters provide the basis for quantitative modeling of the molecular dynamics associated with this vibration. A quantum mechanical calculation permits determination of the quadratic and quartic force constants K66=537(17) and K6666=4.98(12) cm−1 which in turn are used to estimate the pertinent cubic band stretching interaction constants K466=−149.3(50) cm−1 and account for the unexpected behavior in the rotational constant B16. Second order expansion of the vibrational term energies, give X46=−21.61(2), X67=−7.694(1), X66=−14.84(90), g66=−31.04(90) cm−1, neglecting corrections for Fermi resonance. The common isotopic species equilibrium rotational constant Be is evaluated to be 3681.1(11) MHz.