Internal dynamics and HF bond lengthening in the hydrogen-bonded heterodimer CH3CN⋯HF determined from nuclear hyperfine structure in its rotational spectrum

Abstract

Nuclear hyperfine structure has been resolved and analysed in each of the K= 0 and K= 1 components of the J= 2 â†� 1 transitions of the hydrogen-bonded heterodimers CH3C15N⋯HF and CH3C15N⋯DF to give the H, F nuclear spin–nuclear spin coupling constant DHF and the D-nuclear quadrupole coupling constant χD, respectively, of these symmetric top molecules. The additional determination of unperturbed transition frequencies for the K= 0 and K= 1 components of the J= 3 â†� 2 and 4 â†� 3 transitions for each species has allowed an accurate evaluation of the rotational constants B0 and the centrifugal distortion constants DJ and DJK as follows: [graphic omitted]. Analysis of these spectroscopic constants leads to the following molecular properties of CH3CN⋯HF: [graphic omitted].