This resonance has been explicitly treated in the analysis in order to obtain molecular constants with clear physical meaning.Ĭonclusions. Our analysis shows that all HOCO + lines with K a ≥ 3 are perturbed by a ro-vibrational interaction that couples the ground state with the v 5 = 1 vibrationally excited state.
The newly measured lines have significantly enlarged the available data sets for HOCO + and DOCO +, thus enabling the determination of highly accurate rotational and centrifugal distortion parameters. Additionally, 46 line positions taken from the literature have been accurately remeasured. The ground-state spectra of HOCO + and DOCO + have been investigated in the 213–967 GHz frequency range 94 new rotational transitions have been detected. The ions were produced in a low-density, magnetically confined plasma generated in a suitable gas mixture. Ground-state transitions have been recorded in the laboratory using a frequency-modulation absorption spectrometer equipped with a free-space glow-discharge cell.
The aim of this work is to extend the study of the ground-state pure rotational spectra of HOCO + and DOCO + well into the sub-millimetre region. Despite the obvious astrochemical relevance, protonated CO 2 and its deuterated variant, DOCO +, still lack an accurate spectroscopic characterisation.Īims. This cation has been detected towards several lines of sight, including massive star forming regions, protostars, and cold cores. HOCO + is a polar molecule that represents a useful proxy for its parent molecule CO 2, which is not directly observable in the cold interstellar medium.
CaselliĬenter for Astrochemical Studies, Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße 1, 85748 Garching, GermanyĬontext.
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