High-resolution THz gain measurements in optically pumped ammonia

This study is aimed at the evaluation of THz gain properties in an optically pumped NH3 gas. NH3 molecules undergo rotational-vibrational excitation by mid-infrared (MIR) optical pumping provided by a MIR quantum cascade laser (QCL) which enables precise tuning to the NH3 infrared transition around 10.3 mu m. Pure inversion transitions, (J = 3, K = 3) at 1.073 THz and (J = 4, K = 4) at 1.083 THz were selected. The THz measurements were performed using a THz frequency multiplier chain. The results show line profiles with and without optical pumping at different NH3 pressures, and with different MIR tuning. The highest gain at room temperature under the best conditions obtained during single pass on the (3,3) line was 10.1 dBxm(-1) at 26 mu bar with a pumping power of 40 mW. The (4,4) line showed lower gain of 6.4 dBxm(-1) at 34 mu bar with a pumping power of 62 mW. To our knowledge these THz gains are the highest measured in a continuous-wave MIR pumped gas.Web of Science2616212482124

13C—methyl formate : observations of a sample of high mass starforming regions including Orion—KL and spectroscopic characterization

We have surveyed a sample of massive star-forming regions located over a range of distances from the Galactic centre for methyl formate, HCOOCH3, and its isotopologues H13COOCH3 and HCOO13CH3. The observations were carried out with the APEX telescope in the frequency range 283.4-287.4 GHz. Based on the APEX observations, we report tentative detections of the 13C-methyl formate isotopologue HCOO13CH3 towards the following four massive star-forming regions: Sgr B2(N-LMH), NGC 6334 IRS 1, W51 e2 and G19.61-0.23. In addition, we have used the 1 mm ALMA science verification observations of Orion-KL and confirm the detection of the 13C-methyl formate species in Orion-KL and image its spatial distribution. Our analysis shows that the 12C/13C isotope ratio in methyl formate toward Orion-KL Compact Ridge and Hot Core-SW components (68.4±10.1 and 71.4±7.8, respectively) are, for both the 13C-methyl formate isotopologues, commensurate with the average 12C/13C ratio of CO derived toward Orion-KL. Likewise, regarding the other sources, our results are consistent with the 12C/13C in CO. We also report the spectroscopic characterization, which includes a complete partition function, of the complex H13COOCH3 and HCOO13CH3 species. New spectroscopic data for both isotopomers H13COOCH3 and HCOO13CH3, presented in this study, has made it possible to measure this fundamentally important isotope ratio in a large organic molecule for the first time.This work was supported by the National Science Foundation under grant 1008800. We are grateful to the Ministerio de Economia y Competitividad of Spain for the financial support through grant No. FIS2011-28738-C02-02 and to the French Government through grant No. ANR-08-BLAN-0054 and the French PCMI (Programme National de Physique Chimie du Milieu Interstellaire). This paper makes use of the following ALMA data: ADS/JAO. ALMA#2011.0.00009.SV.ALMAis a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. C.F. thanks Dahbia Talbi, Eric Herbst, and Anthony Remijan for enlightening discussions. Finally, we thank the anonymous referee for helpful comments

Spectroscopie millimétrique et submilimétrique de molécules astrophysiques (application au Formiate de Méthyle, au Glycolaldéhyde et à l'Isocyanure d'Allyle)

Les molécules organiques complexes sont abondantes dans le milieu interstellaire et leur détection est indispensable à la compréhension des processus chimiques gouvernant l'univers. Les détections astronomiques sont réalisées par des télescopes comme ALMA, SOFIA, HERSCHEL et IRAM, dans le domaine millimétrique. À cette fin la spectroscopie de rotation en laboratoire est une étape indispensable. L'étude du glycolaldéhyde, de l'isocyanure d'allyle et du formiate de méthyle a été réalisée. Les spectres ont été enregistrés sur le spectromètre millimétrique et submillimétrique du PhLAM. Le glycolaldéhyde est une molécule pré-biotique possible, les états fondamentaux et les trois premiers modes de vibration des deux isotopologues 13C ont été modélisés par le modèle théorique du Hamiltonien de Watson. Le formiate de méthyle, isomère du glycolaldéhyde, est très abondant dans le milieu interstellaire. Il contient un groupe méthyle et est caractérisé par un mouvement de grande amplitude qui se couple avec la rotation globale de la molécule. La modélisation de ce couplage a nécessité un ajustement global des états de torsion t = 0 et 1 du groupe méthyle de l'isotopologue 13C-2. Sa détection dans Orion-KL sera reportée. L'isocyanure d'allyle est d'intérêt astrophysique. Cette molécule présente une structure hyperfine due à l'atome N et résolue uniquement dans le domaine micro-onde. L'analyse des états fondamentaux des conformères Cis et Gauche les plus stables a été entendue dans le domaine millimétrique et submillimétrique. L'interaction de Coriolis (type a et b) entre les niveaux 1 = 1 et 2 = 1 du conformère Cis de l isocyanure d allyle a été modélisée.Complex organic molecules are abundant in the interstellar medium and their detection play a big role in the comprehension of the chemical processes governing the evolution of the universe. Astronomical detection in the millimeter- wave region is realized by the use of telescopes such as ALMA, SOFIA, HERSCHEL and IRAM. For this purpose, rotational spectroscopy in the laboratory is an essential stage. In consequence, the study of glycolaldehyde, allylisocyanide and methylformate was elaborated. The spectrum of these molecules was recorded with the millimeter- and submillimeter- wave spectrometer in the PhLAM laboratory. Glycolaldehyde is a possible prebiotic molecule. The rotational spectra of the ground state and the three lowest vibrational modes for the two 13C isotopologs were modeled by a Watson Hamiltonian. The methylformate is an isomer of glycolaldehyde and is very abundant in the interstellar medium. It is characterized by the presence of methyl group establishing large amplitude motion witch couples with the global rotation of the molecule. To model this interaction for the 13C-2 isotopolog, a global fit of the two torsional states t = 0 et 1 of the methyl group is required. The detection of t = 1 in Orion-KL will be reported. Allylisocyanide is of astrophysical interest. This molecule establishes an hyperfine structure due to the presence of the N atom. This structure is resolved only in the micro- wave domain. The analysis of the ground state of both conformers was extended in the millimeter- and submillimeter- wave regions. Coriolis interactions of a and b types between 1 = 1 and 2 = 1 sates of the Cis conformer was resolved.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Spectroscopie millimétrique et submillimétrique de molécules d'intérêts atmosphérique et/ou astrophysique (développement du spectromètre térahertz de Lille)

La spectroscopie est une source d'informations sur les atmosphères planétaires et cométaires ainsi que sur le milieu interstellaire.Elle permet la détection des composés chimiques, la détermination de leur abondance et de l'excitation de leurs niveaux d'énergie, donnant ainsi accès à la physique et la chimie de ces milieux. L'analyse des spectres en laboratoire dans le domaines infrarouge, microonde, millimétrique et submillimétrique, est une condition nécessaire pour la détetion de nouvelles espèces. Le dernier de ces domaines, appelé aussi Térahertz, est aujourd'hui en plein essor. De multiples avancées technologiques ont eu lieu tant au niveau des sources qu'au niveau des détecteurs. La spectroscopie dans ce domaine est d'autant plus importante que certains projets astrophysiques, tels que Herschel (2007) et ALMA (à partir de 2006), fonctionneront dans le domaine Térahertz. Dans une première partie, les différentes spectromètres, couvrant les domaines infrarouge, microonde et millimétrique, sont décrits. Ensuite les études menées sur l'Éthylène, le Cyano-acétylène 15N et le Formiate de méthyle H13COOCH3, qui sont des molécules d'intérêt astrophysique sont détaillées. Enfin, les résultats obtenus pour l'Ozone et le Chlorure de Vinyle sont présentés. La seconde partie est dédiée au spectromètre Térahertz de Lille. Apparu il y a une quinzaine d'années au laboratoire PhLAM, le fonctionnement de ce spectromètre fait l'objet d'un premier chapitre. Les modifications apportées, telles que le passage à la détection bolométrique, l'extension de la couverture spectrale et l'étude d'une technique de spectroscopie intracavité sont détaillées dans un second chapitre.LILLE1-BU (590092102) / SudocSudocFranceF

MILLIMETER-WAVE SPECTROSCOPY OF AMINOMALONONITRILE

Author Institution: Laboratoire PhLAM, UMR 8523 CNRS - Universite Lille 1, 59655 Villeneuve d'Ascq Cedex, France; Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS - ENSCR, 35708 Rennes Cedex 7, France.This work is supported by the French program "Physique et Chimie du Milieu Interstellaire (PCMI, INSU-CNRS)" and the Centre National d'Etudes Spatiales (CNES).In low-temperature conditions of the interstellar medium pure HCN and mixtures of HCN with H$_2$O and NH$_3$ subjected to high-energy sources can be converted into different HCN polymers, 2004, 170, 203}. In this context the HCN trimer -- aminomalononitrile (AMN, H$_2$NCH(CN)$_2$) is an interesting candidate for astrophysical detection. We measured the rotational spectrum of AMN using the Lille BWO-based fast scan spectrometer (120 -- 180 GHz) and the spectrometer based on solid state sources (225 -- 250 GHz). The spectroscopic work was supported by high level \textit{ab initio} calculations. The spectra observed were assigned only to the asymmetric conformer. The first analysis revealed the regular doublet splittings of rotational lines indicating the possibility of large-amplitude motion (LAM) of amino group. Further examination of the spectra revealed the existence of additional splittings most probably due to the second LAM of amino group. Since the equilibrium structure of AMN has no symmetry, in the group theoretical formalism these two LAMs can be described using G$_4$ permutation-inversion group. Despite the complexity of the LAMs all the assigned rotational transitions were fitted within experimental accuracy using Pickett's SPFIT program. As a result, a reliable dataset for astrophysical observations was provided

THE ROTATIONAL SPECTRUM OF 13^{13}CH3_3NH2_2 UP TO 1 THz

This work is supported by the Programme National de Physico-Chimie du Milieu Interstellaire (PCMI-CNRS) and by the contract ANR-08-BLAN-0054.Author Institution: Laboratoire PhLAM, CNRS UMR 8523, Universite de Lille 1, 59655 Villeneuve d'Ascq Cedex, France; Institute of Radio Astronomy of NASU, Chervonopraporna 4, 61002 Kharkov, UkraineMethylamine (CH$_3$NH$_2$) is a molecule of astrophysical importance detected in interstellar medium for the first time in 1974~{\bf 191} (1974) L135.}. Also it has been discovered in the atmosphere of Jupiter~{\bf 4} (1977) 203. }. It is suggested that methylamine can be a precursor of the simplest amino acid glycine. In this context we present a new study of rotational spectrum of the ground vibrational state of $^{13}$C isotopologue of methylamine in the frequency range up to 1 THz. The spectrum of $^{13}$CH$_3$NH$_2$ was recorded and analyzed for the first time. All the spectra were obtained using the Lille spectrometer based on the solid state sources. The analysis of the rotational spectrum of methylamine is complicated by two large-amplitude motions: CH$_3$ torsion and NH$_2$ wagging. The Hamiltonian used in the present study is based on the group-theoretical high-barrier tunneling formalism developed by Ohashi and Hougen~{\bf 121} (1987) 474.}. This model proved to be efficient in the previous studies of the parent species of methylamine~{\bf 229} (2005) 170.} since it allowed fitting within experimental accuracy all the rotational transitions of the ground vibrational state with $J \leq 30$. In view of extended frequency range of the present study the fitting program will be modified in order to take into account the rotational transitions with $J > 30$. For the parent isotopic species, measurements and analysis using the same approach are in progress. The latest results will be discussed

The hydration of polycyclic aromatic compounds: the case of naphthaldehyde

International audiencePolycyclic aromatic hydrocarbons (PAHs) and their oxygenated products (oxi-PAH) are considered as important pollutants of the Earth’s atmosphere since they are emitted by the combustion of fuels. [1] The study of their intermolecular interactions is essential to understand the formation of their aerosols. In this work, we have studied at molecular level the interactions present in the hydration of the oxi-PAH, α- and β-naphthaldehyde. This study has been performed using a supersonic jet Fourier transform microwave (FTMW) spectrometer in the 4-15 GHz range, with the support of theoretical calculations. Both isolated α- and β-naphthaldehyde species could present two possible structures: cis, the most stable one for α, and trans for β. [2] Our calculations show that there are three low energy monohydrates predicted for each conformer, cis/trans, in an energy range of 1500 cm-1. Experimentally, one conformer has been observed in gas phase for α and two for β, corresponding to the calculated most stable structures. All species are stabilized by intermolecular hydrogen bonds between the water molecule and the aldehyde group of naphthaldehyde: for the α isomer, the oxygen of the aldehyde acts as proton acceptor and the aldehyde hydrogen as proton donor; for the β isomer, the oxygen of the aldehyde acts as proton acceptor and one of the ring hydrogens as a proton donor.[3][1] Karavalakis G. et al. Sci. Tot. Environ., 409, 4, 738, 2011.[2] Goubet M., et al. J. Phys. Chem. A, 124, 4484, 2020.[3] This work is supported by the CaPPA project and by the CPER ClimiBio funded by the French National Research Agency (ANR) through the PIA 11-LABX-0005-01, the I-SITE ULNE/ANR-16-IDEX-0004 ULNE, the Regional Council Hauts-de-France and the European Funds for Regional Economic Development (FEDER)

PROSPECTIVE WORK FOR ALMA: THE MILLIMETERWAVE AND SUBMILLIMETERWAVE SPECTRUM OF 13^{13}C-GLYCOLALDEHYDE

This work is supported by the Programme National de Physico-Chimie du Milieu Interstellaire (PCMI-CNRS) and by the contract ANR-08-BLAN-0054.Author Institution: Laboratoire PhLAM, UMR8523 CNRS-Universite; Lille 1, F-59655 Villeneuve d'Ascq Cedex, France; UMR6226 CNRS-Ecole Nationale; Superieure de Chimie de Rennes,F-35700 Rennes, FranceGlycolaldehyde has been identified in interstellar sources ~{\bf 554}(2001) L81 ; R.~A.~H.~Butler, F.~C.~De~Lucia, D.~T~Petkie, et al., {\em Astrophys.~J.~Supp.}~{\bf 134} (2001) 319 ; M.~T.~Beltran, C.~Codella, S.~Viti, R.~Niri, R.~Cesaroni, {\em Astrophys.~J.}~{\bf 690} (2009) L93.}. The relative abundance ratios of the three isomers (acetic acid) : (glycolaldehyde) : (methylformate) were estimated . The detection of $^{13}$C$_1$ and $^{13}$C$_2$ isotopomers of methylformate has been recently reported in Orion, as a result of the detailled labororatory spectroscopic study~{\bf 500} (2009) 1109.}. Therefore the spectroscopy of the $^{13}$C isotopomers of glycolaldehyde is investigated in laboratory in order to provide data for an astronomical search. The instrument ALMA will certainly be a good instrument to detect them. Up to now, only the microwave spectra of $^{13}$CH$_2$OH-CHO and of CH$_2$OH-$^{13}$CHO have been observed several years ago in the 12-40 GHz range~{\bf 16} (1973) 259.}. Spectra of both species are presently recorded in Lille in the 150-950 GHz range with the new submillimetre-wave spectrometer based on harmonic generation of a microwave synthesizer source, using only solid-state devices, and coupled to a cell of 2.2 m length~{\bf 264} (2010) 94.}. The absolute accuracy of the line positions is better than 30 KHz. The rotational structure of the ground state and of the three first excited vibrational states has been observed. Two $^{13}$C enriched samples were used. The analysis is in progress

SPECTROSCOPY OF THE GROUND, FIRST AND SECOND EXCITED TORSIONAL STATES OF ACETALDEHYDE FROM 0.05 TO 1.6 THz.

Author Institution: Institute of Radio Astronomy of NASU, Chervonopraporna 4, 61002 Kharkov, Ukraine; Laboratoire de Physique des Lasers, Atomes et Molecules, UMR 8523 CNRS-Universite Lille 1, Batiment P5, F-59655 Villeneuve d'Ascq Cedex, France; Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099, USAA new global study of the acetaldehyde (CH${_3}$CHO) spectrum is reported. The new measurements cover the frequency range from 49 GHz to 1.6 THz and have been carried out using three different spectrometers in IRA NASU (Ukraine), PhLAM Lille (France), and JPL (USA). The rotational transitions belonging to the three lowest torsional states, as well as previously published data on the FIR torsional bands, of the molecule have been analyzed using the rho-axis-method. The dataset consisting of more than 19700 line frequencies and including rotational transitions with {\it J} up to 66 and {\it K${_a}$} up to 22 was fit using a model consisting of 117 parameters and weighted root-mean-square deviation of 0.71 has been achieved. Details of this new study and problems encountered in analysis of the second torsional state will be discussed