6533b7d7fe1ef96bd1269138
RESEARCH PRODUCT
Deuterium hyperfine splittings in the rotational spectrum of NH2D as revealed by Lamb-dip spectroscopy
Jürgen GaussMattia MelossoLuca DoreCristina Puzzarinisubject
HydrogenQuantum-chemical calculationschemistry.chemical_elementContext (language use)010402 general chemistry01 natural sciencesSpectral lineDeuterium fractionationAmmoniaInterstellar medium0103 physical sciencesPhysical and Theoretical ChemistrySpectroscopyHyperfine structureSpectroscopyAstrophysics::Galaxy AstrophysicsLine (formation)Physics010304 chemical physicsSpectrometerAtomic and Molecular Physics and Optics0104 chemical sciencesDeuteriumchemistryHyperfine structureAtomic physicsLamb-dip techniquedescription
Abstract In the context of radio-astronomical observations, laboratory experiments constitute a cornerstone in the interpretation of rich line surveys due to the concomitant presence of numerous emitting molecules. Here, we report the investigation of three different rotational transitions of mono-deuterated ammonia (NH2D), a species of astrophysical interest, for which the contribution of the deuterium nuclear spin to the rotational spectrum has been resolved for the first time in the millimeter- and submillimeter-wave domain. The effect of hyperfine interactions on the rotational spectrum has been unveiled by a combined theoretical and experimental approach. Quantum-chemical calculations based on coupled-cluster theory have been employed to evaluate the hyperfine parameters of nitrogen, hydrogen, and deuterium in NH2D. Subsequently, the Lamb-dip technique has been used to investigate the rotational spectrum of NH2D at high-resolution. In detail, three low-J transitions have been recorded at 86, 110, and 333 GHz with a frequency-modulation millimeter-/submillimeter-wave spectrometer. From the line profile analysis of the recorded spectra, the main terms responsible for the rotational hyperfine structure have been determined with good accuracy. Our work allows a comprehensive analysis of the rotational features of NH2D in radioastronomical spectra and a more accurate evaluation of its column density, especially in non-turbulent regions showing narrow linewidths.
year | journal | country | edition | language |
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2020-04-01 |