Searching for Trans Ethyl Methyl Ether in Orion KL

We report on the tentative detection of $trans$ Ethyl Methyl Ether (tEME), $t-CH_3CH_2OCH_3$, through the identification of a large number of rotational lines from each one of the spin states of the molecule towards Orion KL. We also search for $gauche$-$trans$-n-propanol, $Gt-n-CH_3CH_2CH_2OH$, an isomer of tEME in the same source. We have identified lines of both species in the IRAM 30m line survey and in the ALMA Science Verification data. We have obtained ALMA maps to establish the spatial distribution of these species. Whereas tEME mainly arises from the compact ridge component of Orion, Gt-n-propanol appears at the emission peak of ethanol (south hot core). The derived column densities of these species at the location of their emission peaks are $\leq(4.0\pm0.8)\times10^{15} cm^{-2}$ and $\leq(1.0\pm0.2)\times10^{15} cm^{-2}$ for tEME and Gt-n-propanol, respectively. The rotational temperature is $\sim100 K$ for both molecules. We also provide maps of $CH_3OCOH$, $CH_3CH_2OCOH$, $CH_3OCH_3$, $CH_3OH$, and $CH_3CH_2OH$ to compare the distribution of these organic saturated O-bearing species containing methyl and ethyl groups in this region. Abundance ratios of related species and upper limits to the abundances of non-detected ethers are provided. We derive an abundance ratio $N(CH_3OCH_3)/N(tEME)\geq150$ in the compact ridge of Orion.Comment: Accepted in A&A Letter

Submillimeter Wave Study Of Nitrosomethane (ch3no)

The knowledge of synthetic routes of complex organic molecules is still far to be fully understood. The creation of reliable models is particularly challenging. Hollis et al.\footnote{Hollis, J. M.; {\em et al.}, 2006, {\em ApJ}~{\bf 642}, 933} pointed out that the observations of molecular isomers provides an excellent tool to evaluate the hypothesis of the synthetic pathways. Formamide (HC(O)NH$_2$) is an abundant molecule in ISM detected in 1971 in SgrB2\footnote{Rubin, R. H. ; {\em et al.}, 1971, {\em ApJ}~{\bf 169}, L39}. We decided to investigate two isomers of formamide some years ago: formaldoxime and nitrosomethane, like they are interesting ISM targets. Formaldoxime is a classic asymmetrical spinning top, its spectrum does not present any identification difficulties, it has been published recently\footnote{Zou L. ; {\em et al.}, 2021, {\em A\&A}~{\bf 649}, A60}. Concerning nitrosomethane, the methyl top internal rotation should be taken into account, therefore the analysis is not obvious. We have been working on the project for several years. Analysis is performed using the version of RAM36 coded which includes the treatment of the nuclear quadrupole hyperfine structure\footnote{Ilyushin, V.V. {\em et al}, 2010, {\em J. Mol. Spectrosc.}~{\bf 259}, 26}. Up to now the spectroscopic studies are only available up to 40 GHz \footnote{Turner P. H. {\em et al.}, 1978, {\em J. Chem. Soc., Faraday Trans. 2}~{\bf 74}, 533}. We recently recorded the spectra in Lille from 225 to 660 GHz using the bolometric detection in order to improve the signal to noise ratio. The new spectroscopic results will be presented. Its presence in ISM will also be discussed. \em{This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI.

TIMASSS : The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey: Tentative Detection of Deuterated Methyl Formate (DCOOCH3)

High deuterium fractionation is observed in various types of environment such as prestellar cores, hot cores and hot corinos. It has proven to be an efficient probe to study the physical and chemical conditions of these environments. The study of the deuteration of different molecules helps us to understand their formation. This is especially interesting for complex molecules such as methanol and bigger molecules for which it may allow to differentiate between gas-phase and solid-state formation pathways. Methanol exhibits a high deuterium fractionation in hot corinos. Since CH3OH is thought to be a precursor of methyl formate we expect that deuterated methyl formate is produced in such environments. We have searched for the singly-deuterated isotopologue of methyl formate, DCOOCH3, in IRAS 16293-2422, a hot corino well-known for its high degree of methanol deuteration. We have used the IRAM/JCMT unbiased spectral survey of IRAS 16293-2422 which allows us to search for the DCOOCH3 rotational transitions within the survey spectral range (80-280 GHz, 328-366 GHz). The expected emission of deuterated methyl formate is modelled at LTE and compared with the observations.} We have tentatively detected DCOOCH3 in the protostar IRAS 16293-2422. We assign eight lines detected in the IRAM survey to DCOOCH3. Three of these lines are affected by blending problems and one line is affected by calibration uncertainties, nevertheless the LTE emission model is compatible with the observations. A simple LTE modelling of the two cores in IRAS 16293-2422, based on a previous interferometric study of HCOOCH3, allows us to estimate the amount of DCOOCH3 in IRAS 16293-2422. Adopting an excitation temperature of 100 K and a source size of 2\arcsec and 1\farcs5 for the A and B cores, respectively, we find that N(A,DCOOCH3) = N(B,DCOOCH3) ~ 6.10^14 /cm2. The derived deuterium fractionation is ~ 15%, consistent with values for other deuterated species in this source and much greater than that expected from the deuterium cosmic abundance. DCOOCH3, if its tentative detection is confirmed, should now be considered in theoretical models that study complex molecule formation and their deuteration mechanisms. Experimental work is also needed to investigate the different chemical routes leading to the formation of deuterated methyl formate

A line confusion limited millimeter survey of Orion KL (I): sulfur carbon chains

We perform a sensitive (line confusion limited), single-side band spectral survey towards Orion KL with the IRAM 30m telescope, covering the following frequency ranges: 80-115.5 GHz, 130-178 GHz, and 197-281 GHz. We detect more than 14 400 spectral features of which 10 040 have been identified up to date and attributed to 43 different molecules, including 148 isotopologues and lines from vibrationally excited states. In this paper, we focus on the study of OCS, HCS+, H2CS, CS, CCS, C3S, and their isotopologues. In addition, we map the OCS J=18-17 line and complete complementary observations of several OCS lines at selected positions around Orion IRc2 (the position selected for the survey). We report the first detection of OCS v2 = 1 and v3 = 1 vibrationally excited states in space and the first detection of C3S in warm clouds. Most of CCS, and almost all C3S, line emission arises from the hot core indicating an enhancement of their abundances in warm and dense gas. Column densities and isotopic ratios have been calculated using a large velocity gradient (LVG) excitation and radiative transfer code (for the low density gas components) and a local thermal equilibrium (LTE) code (appropriate for the warm and dense hot core component), which takes into account the different cloud components known to exist towards Orion KL, the extended ridge, compact ridge, plateau, and hot core. The vibrational temperature derived from OCS v2 = 1 and v3 = 1 levels is about 210 K, similar to the gas kinetic temperature in the hot core. These OCS high energy levels are probably pumped by absorption of IR dust photons. We derive an upper limit to the OC3S, H2CCS, HNCS, HOCS+, and NCS column densities. Finally, we discuss the D/H abundance ratio and infer the following isotopic abundances: 12C/13C=45+-20, 32S/34S=20+-6, 32S/33S=75+-29, and 16O/18O=250+-135.Comment: Accepted for publication in A&

Re-investigation Of The Cyanoacetaldehyde (ncch2cho) Rotational Spectrum

Cyanoacetaldehyde could be present in interstellar space or in planetary atmospheres, because of the facile hydrolysis of cyanoacetylene, which is prevalent in the interstellar medium, and found in comets and in Titan’s atmosphere. We already studied its rotation spectrum ten years ago\footnote{M\o llendal, H.; {\em et al.}, 2012, {\em J. Phys. Chem. A}~{\bf 116}, 4047}. The two lowest energy rotamers were studied, Rotamer I was found to be 2.9(8) kJ/mol more stable than II by relative intensity measurements. There was no major difficulties with assignment of the conformer II for the ground and the two lowest energy vibrational states. On the other hand, the analysis of the most stable conformer is not satisfactory. This is due to the existence of tunnelling effect between two equivalent configurations, which makes the analysis of the spectra tricky. The assignment is actually limited to data up to 80 GHz and with Ka$<$3. It should be noted that the synthesis of cyanoacetaldehyde is not straightforward, and non negligeable amount of the precursor, isoxazole, is present in the final mixture. We re-examined the millimeter wave spectra (150-330 GHz) as our DDS spectrometer is now faster and particularly suitable for unstable species. We also have more experience with analyzing Coriolis interaction from tunnelling motion.\footnote{Margul\`{e}s, L.; {\em et al.}, 2017, {\em A\&A}~{\bf 601}, A50}. The new spectroscopic results will be presented. Its presence in ISM will also be discussed. \em{This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI.

TIMASSS: The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey. I. Observations, calibration and analysis of the line kinematics

While unbiased surveys observable from ground-based telescopes have previously been obtained towards several high mass protostars, very little exists on low mass protostars. To fill up this gap, we carried out a complete spectral survey of the bands at 3, 2, 1 and 0.8 mm towards the solar type protostar IRAS16293-2422. The observations covered about 200\,GHz and were obtained with the IRAM-30m and JCMT-15m telescopes. Particular attention was devoted to the inter-calibration of the obtained spectra with previous observations. All the lines detected with more than 3 sigma and free from obvious blending effects were fitted with Gaussians to estimate their basic kinematic properties. More than 4000 lines were detected (with sigma \geq 3) and identified, yielding a line density of approximatively 20 lines per GHz, comparable to previous surveys in massive hot cores. The vast majority (~2/3) of the lines are weak and due to complex organic molecules. The analysis of the profiles of more than 1000 lines belonging 70 species firmly establishes the presence of two distinct velocity components, associated with the two objects, A and B, forming the IRAS16293-2422 binary system. In the source A, the line widths of several species increase with the upper level energy of the transition, a behavior compatible with gas infalling towards a ~1 Mo object. The source B, which does not show this effect, might have a much lower central mass of ~0.1 Mo. The difference in the rest velocities of both objects is consistent with the hypothesis that the source B rotates around the source A. This spectral survey, although obtained with single-dish telescope with a low spatial resolution, allows to separate the emission from 2 different components, thanks to the large number of lines detected. The data of the survey are public and can be retrieved on the web site http://www-laog.obs.ujf-grenoble.fr/heberges/timasss.Comment: 41 pages (26 pages of online Tables), 7 Tables and 6 Figure

High resolution spectroscopy of methyltrioxorhenium: towards the observation of parity violation in chiral molecules

Originating from the weak interaction, parity violation in chiral molecules has been considered as a possible origin of the biohomochirality. It was predicted in 1974 but has never been observed so far. Parity violation should lead to a very tiny frequency difference in the rovibrational spectra of the enantiomers of a chiral molecule. We have proposed to observe this predicted frequency difference using the two photon Ramsey fringes technique on a supersonic beam. Promising candidates for this experiment are chiral oxorhenium complexes, which present a large effect, can be synthesized in large quantity and enantiopure form, and can be seeded in a molecular beam. As a first step towards our objective, a detailed spectroscopic study of methyltrioxorhenium (MTO) has been undertaken. It is an ideal test molecule as the achiral parent molecule of chiral candidates for the parity violation experiment. For the 187Re MTO isotopologue, a combined analysis of Fourier transform microwave and infrared spectra as well as ultra-high resolution CO2 laser absorption spectra enabled the assignment of 28 rotational lines and 71 rovibrational lines, some of them with a resolved hyperfine structure. A set of spectroscopic parameters in the ground and first excited state, including hyperfine structure constants, was obtained for the antisymmetric Re=O stretching mode of this molecule. This result validates the experimental approach to be followed once a chiral derivative of MTO will be synthesized, and shows the benefit of the combination of several spectroscopic techniques in different spectral regions, with different set-ups and resolutions. First high resolution spectra of jet-cooled MTO, obtained on the set-up being developed for the observation of molecular parity violation, are shown, which constitutes a major step towards the targeted objective.Comment: 20 pages, 6 figure

SUBMILLIMETER WAVE SPECTROSCOPY FOR ISM: IMINES WITH INTERNAL ROTATION

The aldimines are important to understand amino acids formation process as they appear in reaction scheme of Strecker-type synthesis. It seems reasonable to propose syntheses in the solid phase but the formation process is not clearly established. The number of imines and amines detected in the interstellar medium is limited, mainly due to lack of spectroscopic data. We present here the studies of ethanimine (CH$_{3}$CHNH) and methylimino-acetonitrile (CH$_{3}$N=CHCN). Both of them have has two isomers E and Z with E one being the most stable. These molecules represent a particular case where a quite high (570 and 714 cm$^{-1}$ respectively) internal rotation barrier is combined with relatively a high $\rho$ value (close to 0.3) making analysis of the spectra rather delicate. The fits were performed using a version of RAM36 code\footnote{Ilyushin, V.V. et al;{\em J. Mol. Spectrosc.}~{\bf259}, (2010) 26} which includes the treatment of the nuclear quadrupole hyperfine structure. Ethanimine was detected already in ISM\footnote{Loomis, R. A.; {\em et al.} {\em ApJ. Lett.}~{\bf765},(2013) L9}, but the spectrosocpic analyses were limited to low K$_{a}$ values\footnote{Lovas, F. J.; {\em et al.} {\em J. Chem. Phys.}~{\bf72}, (1980) 4964}$^{,}$\footnote{Melli A.; {\em et al.} {\em ApJ}~{\bf855}, (2018) 123}. In the current study we significantly extend the rotational quantum number coverage for this molecule.\\ The spectroscopic results for both molecules and searches of methylimino-acetonitrile in ISM will be presented.\\ \em{This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI.

SUBMILLIMETER WAVE SPECTROSCOPY AND ISM SEARCH FOR PROPIONIC ACID

Two compounds with a C$_{2}$H$_{4}$O$_{2}$ formula have been detected in the Interstellar Medium (ISM): acetic acid (CH$_{3}$CO$_{2}$H) and methyl formate (CH$_{3}$OC(O)H), the latter being thermodynamically less stable than the former but more abundant. Among the higher homologues with a C$_{3}$H$_{6}$O$_{2}$ formula where a hydrogen atom in C$_{2}$H$_{4}$O$_{2}$ has been replaced by a CH$_{3}$ group, two compounds have already been detected: ethyl formate (EtOC(O)H) and methyl acetate (CH$_{3}$OC(O)CH$_{3}$). The higher thermodynamic stability of another isomer, the propionic acid (EtCO$_{2}$H), pushed us to record its rotational spectrum, since this compound has a high probability of being present in the ISM. The methyl top internal rotation should be taken into account, therefore the analysis is performed using RAM36 code.\footnote{Ilyushin, V.V. et al;{\em J. Mol. Spectrosc.}~{\bf259}, (2010) 26} The spectroscopic results and its search in ISM will be presented.\\ \em{This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI