Simultaneous analysis of rovibrational and rotational data for the 41, 51, 61, 72, 81, 7191 and 92 states of HCOOH

In order to carry out an analysis of the high resolution FTIR spectrum of the ν5 vibrational band of HCOOH, it was found necessary to include in the analysis the seven interacting vibrational states 81, 61, 51, 72, 7191, 92 and 41. New FTIR and MMW–SMMW data, recorded with the FASSST spectrometer, and some previously published data were included in the fit. A complete set of parameters, describing the unperturbed states and the interactions, was obtained. All observed perturbations are accounted for and assignments to high quantum numbers were possible.