THz rotational spectrum of H2F+

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 γ2(a) and the range of the values derived from three pairs of rotational constants.