Terahertz spectroscopy of deuterated formaldehyde using a frequency multiplication chain

Zakharenko, Olena; Motiyenko, R. A.; Margulès, L.; Huet, T. R.

doi:10.1016/j.jms.2015.09.005

Cited by 59 publications

(35 citation statements)

References 25 publications

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“…The first one is the automated millimeter wave spectrometer of the Institute of Radio Astronomy of NASU in Kharkiv, Ukraine (Alekseev et al 2012). The second one is the terahertz spectrometer of the Laboratory of Physics of Lasers, Atoms, and Molecules in Lille, France (Zakharenko et al 2015).…”

Section: Methodsmentioning

confidence: 99%

Rotational spectroscopy, tentative interstellar detection, and chemical modeling of N-methylformamide

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Meshcheryakov

Garrod

et al. 2017

A&A

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Context. N-methylformamide, CH 3 NHCHO, may be an important molecule for interstellar pre-biotic chemistry because it contains a peptide bond, which in terrestrial chemistry is responsible for linking amino acids in proteins. The rotational spectrum of the most stable trans conformer of N-methylformamide is complicated by strong torsion-rotation interaction due to the low barrier of the methyl torsion. For this reason, the theoretical description of the rotational spectrum of the trans conformer has up to now not been accurate enough to provide a firm basis for its interstellar detection. Aims. In this context, as a prerequisite for a successful interstellar detection, our goal is to improve the characterization of the rotational spectrum of N-methylformamide. Methods. We use two absorption spectrometers in Kharkiv and Lille to measure the rotational spectra over the frequency range 45-630 GHz. The analysis is carried out using the Rho-axis method and the RAM36 code. We search for N-methylformamide toward the hot molecular core Sagittarius (Sgr) B2(N2) using a spectral line survey carried out with the Atacama Large Millimeter/submillimeter Array (ALMA). The astronomical spectra are analyzed under the assumption of local thermodynamic equilibrium. The astronomical results are put into a broader astrochemical context with the help of a gas-grain chemical kinetics model. Results. The new laboratory data set for the trans conformer of N-methylformamide consists of 9469 distinct line frequencies with J ≤ 62, including the first assignment of the rotational spectra of the first and second excited torsional states. All these lines are fitted within experimental accuracy for the first time. Based on the reliable frequency predictions obtained in this study, we report the tentative detection of N-methylformamide towards Sgr B2(N2). We find N-methylformamide to be more than one order of magnitude less abundant than formamide (NH 2 CHO), a factor of two less abundant than the unsaturated molecule methyl isocyanate (CH 3 NCO), but only slightly less abundant than acetamide (CH 3 CONH 2 ). We also report the tentative detection of the 15 N isotopologue of formamide ( 15 NH 2 CHO) toward Sgr B2(N2). The chemical models indicate that the efficient formation of HNCO via NH + CO on grains is a necessary step in the achievement of the observed gas-phase abundance of CH 3 NCO. Production of CH 3 NHCHO may plausibly occur on grains either through the direct addition of functional-group radicals or through the hydrogenation of CH 3 NCO. Conclusions. Provided the detection of N-methylformamide is confirmed, the only slight underabundance of this molecule compared to its more stable structural isomer acetamide and the sensitivity of the model abundances to the chemical kinetics parameters suggest that the formation of these two molecules is controlled by kinetics rather than thermal equilibrium.

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Section: Methodsmentioning

confidence: 99%

Rotational spectroscopy, tentative interstellar detection, and chemical modeling of N-methylformamide

Беллоче

Meshcheryakov

Garrod

et al. 2017

A&A

155

261

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“…The H 2 C 17 O entry employed previ-1 http://youngstars.nbi.dk/PILS ous data from Cornet et al (1980b) and from Flygare & Lowe (1965). Entries of the deuterated isotopologues, HDCO, D 2 CO, HD 13 CO, D 13 2 CO, HDC 18 O and D 2 C 18 O, were based on the very recent analyses by Zakharenko et al (2015). The analyses took into account earlier data for five of these six isotopologues (no earlier data for HDC 18 O) from Dangoisse et al (1978) as well as extensive data for HDCO and D 2 CO from Bocquet et al (1999).…”

Section: Laboratory Spectroscopy Datamentioning

confidence: 99%

The ALMA-PILS Survey: Formaldehyde deuteration in warm gas on small scales toward IRAS 16293–2422 B

Persson

Jørgensen

Müller

et al. 2018

A&A

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Context. The enhanced degrees of deuterium fractionation observed in envelopes around protostars demonstrate the importance of chemistry at low temperatures, relevant in pre-and protostellar cores. Formaldehyde is an important species in the formation of methanol and more complex molecules. Aims. Here, we present the first study of formaldehyde deuteration on small scales around the prototypical low-mass protostar IRAS 16293−2422 using high spatial and spectral resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations. We determine the excitation temperature, abundances and fractionation level of several formaldehyde isotopologues, including its deuterated forms. Methods. Excitation temperature and column densities of formaldehyde in the gas close to one of the components of the binary are constrained through modeling of optically thin lines assuming local thermodynamical equilibrium. The abundance ratios are compared to results from previous single dish observations, astrochemical models and local ISM values. Results. Numerous isotopologues of formaldehyde are detected, among them H 2 C 17 O, and D 13 2 CO for the first time in the ISM. The large range of upper energy levels covered by the HDCO lines help constrain the excitation temperature to 106±13 K. Using the derived column densities, formaldehyde shows a deuterium fractionation of HDCO/H 2 CO=6.5±1%, D 2 CO/HDCO=12.8 +3.3 −4.1 %, and D 2 CO/H 2 CO=0.6(4)±0.1%. The isotopic ratios derived are 16 O/ 18 O=805 +43 −79 , 18 O/ 17 O=3.2 +0.2 −0.3 and 12 C/ 13 C=56 +8 −11. Conclusions. The HDCO/H 2 CO ratio is lower than found in previous studies, highlighting the uncertainties involved in interpreting single dish observations of the inner warm regions. The D 2 CO/HDCO ratio is only slightly larger than the HDCO/H 2 CO ratio. This is consistent with formaldehyde forming in the ice as soon as CO has frozen onto the grains, with most of the deuteration happening towards the end of the prestellar core phase. A comparison with available time-dependent chemical models indicates that the source is in the early Class 0 stage.

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“…The spectrum of MTO was recorded in the 150-300 GHz range on the Lille millimeter-wave spectrometer 21 at room temperature (294 K), with a vapour pressure of about 20 bar. The frequency source is a 20-GHz synthesizer (Agilent, model E8257D), stabilized on the Global Positioning System.…”

Section: Ii-1 Millimetre-wave Experiments: Room Temperature Millimetrmentioning

confidence: 99%

Characterising molecules for fundamental physics: an accurate spectroscopic model of methyltrioxorhenium derived from new infrared and millimetre-wave measurements

Asselin

Berger

Huet

et al. 2017

Phys. Chem. Chem. Phys.

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Following our first paper about high resolution spectroscopy of methyltrioxorhenium (MTO) [Stoeffler et al. PCCP, 13, 854, (2011)], the present study reports a deeper investigation of the ground state, and Re=O antisymmetric (as) and symmetric (s) stretching excited states of both CH3 187 ReO3 and CH3 185 ReO3 isotopologues, thanks to new devices implemented within our consortium. We carry out high resolution millimeter-wave (MMW) and infrared (IR) spectroscopy in room temperature absorption cells, in a pulsed supersonic jet and in a cryogenic buffer gas cell. This collection of sensitive spectrometers enables us to probe both levels of a vibrational transition in low and room temperature gaseous environments. We thus report a new series of measurements providing particularly accurate rotational and rovibrational data for such a large and heavy organometallic molecule that is solid at room temperature.The combination of the new MMW and IR data leads to an improvement of the rovibrational model of MTO: (i) rotational spectra are extended to the 150-300 GHz range and are analyzed to characterize the ground state rotational and hyperfine structure up to J = 43 and K = 41, resulting in the significant refinement of rotational, quartic and hyperfine parameters, as well as the determination of sextic parameters and a centrifugal distortion correction to the quadrupolar hyperfine constant,(ii) rovibrational data recorded at very different temperatures (between 6 and 300 K) in the 970-1015 cm -1 range, at resolutions down to 8 MHz and frequency accuracies as high as 30 MHz (using the buffer gas technique), are used in a first step to extract more precise excited-state rotational, Coriolis and quartic parameters as well as the ground-state centrifugal distortion parameter of the 187 Re isotopologue, which isn't accessible from rotational spectroscopy alone. In a second step, taking the hyperfine structure into account, the upper state rhenium atom quadrupole coupling constant eQq' is determined from the assignment of partially hyperfine-resolved CO2 laser absorption spectra of a skimmed molecular beam.* now at National Physical Laboratory, Teddington, TW11 0LW, UK. 2 IIntroductionThere is an increasing demand for precision spectroscopy of polyatomic molecules. For example, precise knowledge of molecular constants is required for modeling atmospheres, whether it be our own 1,2 or those found in exo-planets 3 and in the interstellar medium 4 , for studying collision physics 5,6 , and as crucial groundwork for performing fundamental physics tests 7,8,9,10,11,12,13,14,15,16,17 . One such test is the measurement of the parity-violating (PV) energy difference between opposite enantiomers of a chiral molecule, induced by the weak interaction. 18 The chiral derivatives of methyltrioxorhenium (MTO) are excellent candidate species for this measurement, because calculations predict relatively large PV energy differences, and because it is possible to synthesize these molecules and bring them into the gas phase. 8,17,19,20 In...

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Terahertz spectroscopy of deuterated formaldehyde using a frequency multiplication chain

Cited by 59 publications

References 25 publications

Rotational spectroscopy, tentative interstellar detection, and chemical modeling of N-methylformamide

Rotational spectroscopy, tentative interstellar detection, and chemical modeling of N-methylformamide

The ALMA-PILS Survey: Formaldehyde deuteration in warm gas on small scales toward IRAS 16293–2422 B

Characterising molecules for fundamental physics: an accurate spectroscopic model of methyltrioxorhenium derived from new infrared and millimetre-wave measurements

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