FTIR spectra of the ν6 and ν8 bands of 13C formic acid molecule-Assignment of FIR-laser lines

Two interacting vibrational modes ν6 and ν8 of 13C species of formic acid have been studied with high resolution FTIR spectroscopy in the range 900-1300 cm−1 with an instrumental resolution of 0.0018 cm−1. More than 10 000 lines have been assigned and fitted with a RMS deviation of 0.00024 cm−1. The band centers, as well as the rotational, quartic and sextic centrifugal distortion parameters and 6 interaction parameters have been determined. The obtained parameters have enabled the assignments of 24 FIR laser emissions of this molecule observed previously by Dangoisse and Glorieux [D. Dangoisse, P. Glorieux, J. Mol. Spectrosc. 92 (1982) 283-297], Luis et al. [G.M.R.S. Luis, E.M. Telles, A. Scalabrin, D. Pereira, IEEE J. Quantum. Electron. QE-34 (1998) 767-769], and Bertolini et al. [A. Bertolini, G. Carelli, C.A. Massa, A. Moretti, F. Strumia, Infrared Phys. Technol. 40 (1999) 33-36].