The high resolution infrared spectrum and molecular structure of the superacid H2F+ by velocity modulation laser absorption spectroscopy

The gas phase infrared spectrum of the fluoronium ion (H2F+) was recorded with Doppler-limited resolution between 3080 and 3520 cm−1 by velocity modulation laser absorption spectroscopy of a hydrogen plasma containing 5% HF. One hundred and nine of the observed transitions were assigned to the symmetric stretch (ν1) and 217 to the asymmetric (ν3) stretch. A least squares analysis of ν3 transitions up to J=11 and Ka=6 and ν1 transitions up to Ka=4 with Watson’s S-reduced Hamiltonian yielded rotational constants and centrifugal distortion constants for the vibronic ground state and for the two excited states. Small Coriolis interactions between ν1 and ν3 levels were observed, but were not treated explicitly. The band origins for ν3 and ν1 are 3334.6895(26) and 3348.7078(36) cm−1, respectively. The r0 structure of H2F+ was determined as: rHF=0.9577 Å <HFH=114.55°.