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

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.