The millimeter wave spectrum of cis-HCOOH in the ground state and in the v9=1 and v7=1 excited vibrational states, and cis-H13COOH in the ground state

A broadband recording of the millimeter/submillimeter wave spectrum of formic acid heated to 170 °C with the FASSST spectrometer has yielded a multitude of rotational transitions of HCOOH in excited vibrational states. These include transitions of the cis-rotamer, the analysis of which is reported here. The data for the ground state could be significantly extended (546 lines), and the first information on rotational structure in vibrationally excited cis-HCOOH in the v9=1 and v7=1 states was obtained. Finally, transitions of cis-H13COOH in the ground state were also observed. The rotational parameters resulting from the analysis of each of these spectra are reported, together with an initial determination of the Coriolis coupling parameters for the 71/91resonance interaction, an experimental force field calculation and a new structure determination.