Studies of low-frequency intermolecular hydrogen-bonded vibrations using a continuous supersonic slit jet mid-infrared quantum cascade laser spectrometer

Abstract

Rovibrational manifolds in low frequency intermolecular vibrations of prototypical hydrogen-bonded interactions OC–HX (X=F, Cl, CN) are reported using a near infrared quantum cascade cw supersonic jet spectrometer. (i) OC–HCl is studied to evaluate future capabilities of the QCL spectrometer. (ii) Analysis of OC–HF demonstrates applicability to vibrations greater than 80cm−1 above the ground state. ν51 band origins in OC–1H35Cl and OC–1H19F are 48.9944(2) and 81.96825(12)cm−1 respectively. (iii) The corresponding intermolecular ν71 band origin of OC–HCN is 34.63742(18)cm−1 and its corresponding rovibrational spectrum made available for attempted detection in interstellar space. Analysis of ν2, ν2+ν71-ν71, ν2+ν71, and ν2+ν61 vibrations in OC–HCN also enables generation of its 5-dimensional semi-empirical intermolecular potential. Structural and other properties of OC–HCN are then compared with corresponding properties predicted using morphed potentials for the homologous series OC–HX (X=F, Cl, Br, I). These results permit investigation of blue shifts in OC vibrations for this homologous series.