The gas phase infrared spectrum of ν1 and ν1−ν4 HCN---HF

Abstract

A continuously tunable single frequency color center laser has been used to investigate the rovibrational static gas phase infrared spectra of the ν₁ (H–F stretching vibration) and its hot bands ν₁+ν¹₇ −ν¹₇ and ν₁+ν₄−ν₄ in the linear dimer HCN‐‐‐HF. Observed perturbations in the ν₁ and ν₁+ν¹₇ −ν¹₇ subbands results from Coriolis interactions of the excited vibrational states ν₁ and ν₁+ν¹₇ with ν₂+2ν₄+ν¹₇ and ν₂+2ν₄+2ν⁰₇ , respectively. The influence of Coriolis interactions and vibrationally predissociating excited state lifetimes of 1.06(10)×10⁻¹⁰ s are considered in simulation of the observed band profiles. Molecular and anharmonic cross term parameters associated with investigated vibrational states are also presented. Anharmonic crossterms X^○₁₄ , X^○₁₇ , and X^○₄₇ are evaluated as 8.0252(73), 4.2162(53), and 1.000(49) cm⁻¹, from the available data, including the analysis from the unresolved spectra of ν₁−ν₄ and ν₁−ν₄+ν¹₇ −ν¹₇ . The differences of the band origins in ν₁ and ν₁−ν₄ give a value of ν₄=168.344(21) cm⁻¹ for the local spacing of the low frequency hydrogen‐bond stretching vibration.