FTIR Spectroscopy of Three Fundamental Bands of H2F+

The ν1, ν2, and ν3 bands of H2F+ were observed with a Fourier transform absorption spectroscopic technique in the 3 and 7 μm regions. The ion was produced with a hollow cathode discharge in a F2, He, and H2 gas mixture. A simultaneous analysis of FT data combined with laser spectroscopic data was carried out using the Watson’s A-reduced Hamiltonian to determine molecular constants in vibrationally excited states. The effect of the vibration–rotation interaction between the ν1 and ν3 states was found to be small compared with the case of H2O. The vibration–rotation transitions of the ν2 band were first identified and analyzed to obtain molecular constants in the ν2 state, and the band origin was determined to be 1370.5236 (7) cm–1 with one standard deviation in parentheses. Determined molecular constants can be used to derive the re structure of H2F+ as re(H–F) = 0.9608(6) Å, ∠e(H–F–H) = 112.2(2)° with the error corresponding to the uncertainty of the assumed vibration rotation constant γ2a and the range of the values derived from three pairs of rotational constants.