Microwave spectrum of formic acid and its isotopic species in D, 13C and 18O. Study of Coriolis resonances between ν 7 and ν 9 vibrational excited states

Abstract

In the investigation of the 8 → 280 GHz region, 241 and 57 transitions of H 12COOH and DCOOH, respectively, have been assigned to the ν 7 and ν 9 vibrational states coupled by a strong Coriolis resonance. The numerical analysis based on Watson's theory of centrifugal distortion coupled with the addition of Coriolis interaction allows us to obtain a set of parameters which fits the transitions well. The rotational spectra of the isotopic species HCOOD and DCOOD have also been investigated. In this investigation 55 and 67 transitions have been assigned to the ν 7 and ν 9 vibrational states of these two molecules, respectively. A very weak Coriolis resonance was detected. Two non-rigid independent rotors were thus employed and gave us a set of parameters which fits the transitions quite well. The rotational spectrum of the ground state of H 12COOH, H 13COOH, HCOOD, DCOOH, H 12C 16O 18OH, and H 12C 18O 16OH have been reinvestigated and a set of improved parameters was obtained for each species.