scholarly journals Rotational spectroscopy of imidazole: improved rest frequencies for astrophysical searches

2019 ◽  
Vol 628 ◽  
pp. A53
Author(s):  
B. M. Giuliano ◽  
L. Bizzocchi ◽  
A. Pietropolli Charmet ◽  
B. E. Arenas ◽  
A. L. Steber ◽  
...  
Keyword(s):  
Spectroscopic Constants ◽  
Rotational Spectrum ◽  
Star Forming ◽  
Star Forming Regions ◽  
Ring Compounds ◽  
Molecular Core ◽  
Wave Region ◽  
Centrifugal Distortion Constants ◽  
High Level ◽  
The University

Context. Organic ring compounds play a key role in terrestrial biochemistry, and they were also most likely pivotal ingredients in Earth’s prebiotic chemistry. The five-membered ring imidazole, c-C3N2H4, is a substructure of fundamental biological molecules such as the purine nucleobases and the amino acid histidine. An unsuccessful search for imidazole in a sample of cold-core clouds and massive star-forming regions was performed almost 40 years ago. At that time, the spectroscopic knowledge of this species was scarce: the existing laboratory study was limited to the centimetre-wave region, and the precision of the rest frequencies in the millimetre regime was not adequate. Aims. The goal of the present work is to perform a comprehensive investigation of the rotational spectrum of imidazole in its ground vibrational state from the microwave region to the 1 mm wavelength regime. Methods. The rotational spectrum of imidazole was recorded in selected frequency regions from 2 to 295 GHz. These intervals were covered using various broadband spectrometers developed at DESY (Hamburg) and at the University of Virginia. High-level ab initio calculations were performed to obtain reliable estimates of the quartic and sextic centrifugal distortion constants. We used the EMoCA imaging spectral line survey to search for imidazole towards the hot molecular core Sgr B2(N2). Results. About 700 rotational transitions spanning a J interval from 0 to 59 and Kc interval from 0 to 30 were analysed using the Watson S-reduced Hamiltonian. These new data allowed the determination of a much extended set of spectroscopic parameters for imidazole in its vibrational ground state. The improved spectral data allow us to set an upper limit to the column density of imidazole in Sgr B2(N2). Its non-detection implies that it is at least 3400 times less abundant than ethyl cyanide in this source. Conclusions. With the new set of spectroscopic constants, it has been possible to compute reliable rest frequencies at millimetre wavelengths. We suggest a search for imidazole towards TMC-1, where the aromatic molecule benzonitrile was recently detected.

scholarly journals Millimeter wave spectra of ethyl isocyanate and searches for it in Orion KL and Sagittarius B2

2018 ◽  
Vol 616 ◽  
pp. A173 ◽  
Author(s):  
L. Kolesniková ◽  
E. R. Alonso ◽  
B. Tercero ◽  
J. Cernicharo ◽  
J. L. Alonso
Keyword(s):  
Millimeter Wave ◽  
High Mass ◽  
Mass Star ◽  
Rotational Spectrum ◽  
Torsional Mode ◽  
Star Forming ◽  
Star Forming Regions ◽  
Ethyl Isocyanate ◽  
Wave Region ◽  
Centrifugal Distortion Constants

Context. Relatively high abundances of methyl isocyanate (CH3NCO), a methyl derivative of isocyanic acid (HNCO), found in the Orion KL and Sgr B2 molecular clouds suggest that its ethyl derivative, ethyl isocyanate (CH3CH2NCO), may also be present. Aims. The aim of this work is to provide accurate experimental frequencies of ethyl isocyanate in its ground and excited vibrational states in the millimeter wave region to support searches for it in the interstellar medium. Methods. The rotational spectrum of ethyl isocyanate was recorded at room temperature from 80 to 340 GHz using the millimeter wave spectrometer in Valladolid. Assigned rotational transitions were analyzed using the S -reduced semirigid-rotor Hamiltonian. Results. More than 1100 distinct frequency lines were analyzed for the ground vibrational state of the cis conformer as well as for three vibrational satellites corresponding to successive excitation of the lowest-frequency C–N torsional mode. Newly determined rotational and centrifugal distortion constants were used for searches of spectral features of ethyl isocyanate in Orion KL and Sgr B2 clouds. Upper limits to CH3CH2NCO in these high-mass star-forming regions were obtained.

scholarly journals Accurate rest frequencies for propargylamine in the ground and low-lying vibrational states

2018 ◽  
Vol 615 ◽  
pp. A176 ◽  
Author(s):  
C. Degli Esposti ◽  
L. Dore ◽  
C. Puzzarini ◽  
M. Biczysko ◽  
J. Bloino ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Organic Molecules ◽  
Coupling Constants ◽  
Spectroscopic Constants ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Vibrational States ◽  
Important Species ◽  
Centrifugal Distortion Constants ◽  
High Level

Context. To date, several complex organic molecules have been detected in the interstellar medium, and they have been suggested as precursors of biologically important species. Propargylamine (HC ≡C−CH2−NH2) is structurally similar to a number of other organic molecules which have already been identified by radioastronomy, making it a good candidate for astrophysical detection. Aims. This work provides accurate rest frequencies of propargylamine, from the centimeter-wave to the submillimeter-wave region, useful to facilitate the detection of this molecule in the interstellar medium. Methods. An extensive laboratory study of the rotational spectrum of propargylamine has been performed using a pulsed-jet Fourier Transform Microwave (FTMW) spectrometer (7–19 GHz frequency range) and a frequency modulation microwave spectrometer (75–560 GHz). Several hundred rotational transitions of propargylamine were recorded in the ground and three lowest excited vibrational states. The experiments were supported by high-level ab initio computations, mainly employed to characterize the vibrational state structure and to predict spectroscopic parameters unknown prior to this study. Results. The measured transition frequencies yielded accurate rotational constants and the complete sets of quartic and sextic centrifugal distortion constants for propargylamine in its vibrational ground state. 14N-nuclear quadrupole coupling constants were also determined. Rotational and quartic centrifugal distortion constants were also obtained for the low-lying excited states v13 = 1 (A′), v20 = 1 (A″), and v21 = 1 (A″). The a-type Coriolis resonance which couples the v13 = 1 and v21 = 1 levels was analyzed. Conclusions. The determined spectroscopic constants allowed for the compilation of a dataset of highly accurate rest frequencies for astrophysical purposes in the millimeter and submillimeter regions with 1σ uncertainties that are smaller than 0.050 MHz, corresponding to 0.03 km s−1 at 500 GHz in radial equivalent velocity.

scholarly journals Laboratory rotational spectrum and astronomical search for methoxyacetaldehyde

2018 ◽  
Vol 619 ◽  
pp. A67 ◽  
Author(s):  
L. Kolesniková ◽  
I. Peña ◽  
E. R. Alonso ◽  
B. Tercero ◽  
J. Cernicharo ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
Ethyl Formate ◽  
High Mass ◽  
Spectroscopic Constants ◽  
Mass Star ◽  
Rotational Spectrum ◽  
Stable Conformer ◽  
Dark Cloud ◽  
Star Forming ◽  
Star Forming Regions

Context. Methoxyacetaldehyde belongs to a group of structural isomers with the general formula C3H6O2, of which methyl acetate and ethyl formate are known interstellar molecules. Rotational data available for methoxyacetaldehyde are limited to 40 GHz, which makes predictions at higher frequencies rather uncertain.Aims. The aim of this work is to provide accurate experimental frequencies of methoxyacetaldehyde in the millimeter-wave region to support its detection in the interstellar medium.Methods. The rotational spectrum of methoxyacetaldehyde was recorded at room-temperature from 75 to 120 GHz and from 170 to 310 GHz using the millimeter-wave spectrometer in Valladolid. Additional measurements were also performed at conditions of supersonic expansion from 6 to 18 GHz. The assigned rotational transitions were analyzed using theS-reduced semirigid-rotor Hamiltonian.Results. We newly assigned over 1000 lines for the most stable conformer of methoxyacetaldehyde in its ground state and five lowest excited vibrational states, and precise sets of spectroscopic constants were obtained. We searched for spectral features of methoxyacetaldehyde in the high-mass star-forming regions Orion KL and Sagittarius B2, as well as in the cold dark cloud Barnard 1 (B1-b). No lines belonging to methoxyacetaldehyde were detected above the detection limit of our data. We provide upper limits to the methoxyacetaldehyde colum density in these sources.

scholarly journals Submillimeter spectroscopy and astronomical searches of vinyl mercaptan, C2H3SH

2019 ◽  
Vol 623 ◽  
pp. A167 ◽  
Author(s):  
M.-A. Martin-Drumel ◽  
K. L. K. Lee ◽  
A. Belloche ◽  
O. Zingsheim ◽  
S. Thorwirth ◽  
...  
Keyword(s):  
Vinyl Alcohol ◽  
Spectroscopic Constants ◽  
Experimental Investigations ◽  
Rotational Spectrum ◽  
Test Bed ◽  
Frequency Multiplication ◽  
Star Forming ◽  
Astronomical Surveys ◽  
Radiofrequency Discharge ◽  
Upper Limits

Context. New laboratory investigations of the rotational spectrum of postulated astronomical species are essential to support the assignment and analysis of current astronomical surveys. In particular, considerable interest surrounds sulfur analogs of oxygen-containing interstellar molecules and their isomers. Aims. To enable reliable interstellar searches of vinyl mercaptan, the sulfur-containing analog to the astronomical species vinyl alcohol, we investigated its pure rotational spectrum at millimeter wavelengths. Methods. We extended the pure rotational investigation of the two isomers syn and anti vinyl mercaptan to the millimeter domain using a frequency-multiplication spectrometer. The species were produced by a radiofrequency discharge in 1,2-ethanedithiol. Additional transitions were remeasured in the centimeter band using Fourier-transform microwave spectroscopy to better determine rest frequencies of transitions with low-J and low-Ka values. Experimental investigations were supported by quantum chemical calculations on the energetics of both the [C2,H4,S] and [C2,H4,O] isomeric families. Interstellar searches for both syn and anti vinyl mercaptan as well as vinyl alcohol were performed in the EMoCA spectral line survey carried out toward Sgr B2(N2) with ALMA. Results. Highly accurate experimental frequencies (to better than 100 kHz accuracy) for both syn and anti isomers of vinyl mercaptan are measured up to 250 GHz; these deviate considerably from predictions based on extrapolation of previous microwave measurements. Reliable frequency predictions of the astronomically most interesting millimeter-wave lines for these two species can now be derived from the best-fit spectroscopic constants. From the energetic investigations, the four lowest singlet isomers of the [C2,H4,S] family are calculated to be nearly isoenergetic, which makes this family a fairly unique test bed for assessing possible reaction pathways. Upper limits for the column density of syn and anti vinyl mercaptan are derived toward the extremely molecule-rich star-forming region Sgr B2(N2) enabling comparison with selected complex organic molecules.

Rotational Spectrum of Aminoborane: Centrifugal Distortion Constants and Boron and Nitrogen Hyperfine Structure

1991 ◽  
Vol 46 (9) ◽  
pp. 770-776 ◽  
Author(s):  
Kirsten Vormann ◽  
Helmut Dreizler ◽  
Jens Doose ◽  
Antonio Guarnieri
Keyword(s):  
Hyperfine Structure ◽  
Spin Rotation ◽  
Coupling Constants ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Rotational Spectra ◽  
Quadrupole Coupling ◽  
Wave Region ◽  
Nuclear Quadrupole ◽  
Centrifugal Distortion Constants

AbstractThe boron and nitrogen hyperfine structure in the rotational spectra of two aminoborane isotopomers, 11 BH2NH2 and 10BH2NH2, has been investigated and the quadrupole coupling constants of boron 10B, 11B and nitrogen 14N have been determined. We get the following results for the nuclear quadrupole coupling constants: χaa(11B) = -1.684 (14) MHz, χbb(11B) = -2.212 (11) MHz, χcc(11B) = 3.896(11) MHz, χaa(10B) = -3.481 (11) MHz, χbb(10B) = -4.623 (14) MHz, χCC(10B) = 8.104 (14) MHz and xaa(14N) = 0.095 (9) MHz, χbb(14N) = 2.091 (8) MHz, χcf4 (14N)=-2.186 (8) MHz. These nitrogen quadrupole coupling constants are those of the 11BH2 NH2 isotopomer. Additionally we were able to determine two out of the three spin rotation coupling constants caa, cbb, and ccc of boron, caa(11 B = 55.2 (26) kHz, cbb(11B) = 6.62 (36) kHz, caa (10B) = 15.26 (69) kHz and cbb(10B) = 4.94 (70) kHz. The spin rotation coupling constants ccc had to be fixed to zero in both cases. Furthermore we measured the rotational spectra in the mm-wave region to determine all quartic and several sextic centrifugal distortion constants according to Watson's A and S reduction

scholarly journals Rotational spectroscopy and astronomical search for glutaronitrile

2020 ◽  
Vol 636 ◽  
pp. A33
Author(s):  
C. Cabezas ◽  
C. Bermúdez ◽  
Y. Endo ◽  
B. Tercero ◽  
J. Cernicharo
Keyword(s):  
Fourier Transform ◽  
Supersonic Jet ◽  
Rotational Spectrum ◽  
Millimetre Wave ◽  
Quantum Numbers ◽  
Upper Limits ◽  
Quadrupole Coupling ◽  
Centrifugal Distortion Constants ◽  
High Level ◽  
Total Column

Context. Nitriles constitute almost 15% of the molecules observed in the interstellar medium (ISM), surprisingly only two dinitriles have been detected in the ISM so far. The lack of astronomical detections for dinitriles may be partly explained by the absence of laboratory rotational spectroscopic data. Aims. Our goal is to investigate the rotational spectrum of glutaronitrile, N≡C−CH2−CH2−CH2−C≡N, in order to allow its possible detection in the ISM. Methods. The rotational spectrum of glutaronitrile was measured using two different experimental setups. A Fourier transform microwave spectrometer was employed to observe the supersonic jet rotational spectrum of glutaronitrile between 6 and 20 GHz. In addition, the mmW spectrum was observed in the frequency range 72−116.5 GHz using a broadband millimetre-wave spectrometer based on radio astronomy receivers with fast Fourier transform backends. The spectral searches were supported by high-level ab initio calculations. Results. A total of 111 rotational transitions with maximum values of J and Ka quantum numbers 54 and 18, respectively, were measured for the gg conformer of glutaronitrile. The analysis allowed us to accurately determine the rotational, nuclear quadrupole coupling, quartic and sextic centrifugal distortion constants. These rotational parameters were employed to search for glutaronitrile in the cold and warm molecular clouds Orion KL, Sgr B2(N), B1-b and TMC-1, using the spectral surveys captured by IRAM 30 m at 3 mm. Glutaronitrile was not detected, and the upper limits’ column densities were derived. Those are a factor of 1.5 and 5 lower than those obtained for the total column densities of the analogous succinonitrile in Orion KL and Sgr B2, respectively.

scholarly journals Deuterated methyl mercaptan (CH3SD): Laboratory rotational spectroscopy and search toward IRAS 16293–2422 B

2019 ◽  
Vol 621 ◽  
pp. A114 ◽  
Author(s):  
Olena Zakharenko ◽  
Frank Lewen ◽  
Vadim V. Ilyushin ◽  
Maria N. Drozdovskaya ◽  
Jes K. Jørgensen ◽  
...  
Keyword(s):  
Rotational Spectroscopy ◽  
Mass Star ◽  
Methyl Mercaptan ◽  
Rotational Spectrum ◽  
Star Forming ◽  
Star Forming Regions ◽  
Millimeter Wavelengths ◽  
Low Mass ◽  
Line Survey ◽  
Telescope Arrays

Methyl mercaptan (also known as methanethiol), CH3SH, has been found in the warm and dense parts of high- as well as low- mass star-forming regions. The aim of the present study is to obtain accurate spectroscopic parameters of the S-deuterated methyl mercaptan CH3SD to facilitate astronomical observations by radio telescope arrays at (sub)millimeter wavelengths. We have measured the rotational spectrum associated with the large-amplitude internal rotation of the methyl group of methyl mercaptan using an isotopically enriched sample in the 150−510 GHz frequency range using the Köln millimeter wave spectrometer. The analysis of the spectra has been performed up to the second excited torsional state. We present modeling results of these data with the RAM36 program. CH3SD was searched for, but not detected, in data from the Atacama Large Millimeter/submillimeter Array (ALMA) Protostellar Interferometric Line Survey (PILS) of the deeply embedded protostar IRAS 16293−2422. The derived upper limit corresponds to a degree of deuteration of at most ∼18%.

scholarly journals Submillimeter-wave spectroscopy and the radio-astronomical investigation of propynethial (HC≡CCHS)

2020 ◽  
Vol 642 ◽  
pp. A206 ◽  
Author(s):  
L. Margulès ◽  
B. A. McGuire ◽  
C. J. Evans ◽  
R. A. Motiyenko ◽  
A. Remijan ◽  
...  
Keyword(s):  
Rotational Spectrum ◽  
Star Forming ◽  
Rotational Spectra ◽  
Dark Clouds ◽  
Star Forming Regions ◽  
Quantum Numbers ◽  
Good Target ◽  
Upper Limits ◽  
Unambiguous Detection ◽  
Sulfur Containing

Context. The majority of sulfur-containing molecules detected in the interstellar medium (ISM) are analogs of oxygen-containing compounds. Propynal was detected in the ISM in 1988, hence propynethial, its sulfur derivative, is a good target for an ISM search. Aims. Our aim is to measure the rotational spectrum of propynethial and use those measurements to search for this species in the ISM. To date, measurements of the rotational spectra of propynethial have been limited to a small number or transitions below 52 GHz. The extrapolation of the prediction to lines in the milimeter-wave domain is inaccurate and does not provide data to permit an unambiguous detection. Methods. The rotational spectrum was re-investigated up to 630 GHz. Using the new prediction lines of propynethial, as well as the related propynal, a variety of astronomical sources were searched, including star-forming regions and dark clouds. Conclusions. A total of 3288 transitions were newly assigned and fit together with those from previous studies, reaching quantum numbers up to J = 107 and Ka = 24. Watson’s symmetric top Hamiltonian in the Ir representation was used for the analysis, because the molecule is very close to the prolate limit. The search for propynethial resulted in a non-detection; upper limits to the column density were derived in each source.

scholarly journals The millimeter-wave spectrum of methyl ketene and the astronomical search for it

2018 ◽  
Vol 619 ◽  
pp. A92 ◽  
Author(s):  
C. Bermúdez ◽  
B. Tercero ◽  
R. A. Motiyenko ◽  
L. Margulès ◽  
J. Cernicharo ◽  
...  
Keyword(s):  
Excited State ◽  
Millimeter Wave ◽  
Ground State ◽  
Wave Spectrum ◽  
High Mass ◽  
Mass Star ◽  
Rotational Spectrum ◽  
Star Forming ◽  
Dark Clouds ◽  
Star Forming Regions

Context. The analysis of isomeric species of a compound observed in the interstellar medium (ISM) is a useful tool to understand the chemistry of complex organic molecules. It could, likewise, assist in the detection of new species. Aims. Our goal consists in analyzing one of the two most stable species of the C3H4O family, methyl ketene, whose actual rotational parameters are not precise enough to allow its detection in the ISM. The obtained parameters will be used to search for it in the high-mass star-forming regions Orion KL and Sagittarius B2, as well as in the cold dark clouds TMC-1 in the Taurus Molecular Cloud and Barnard 1 (B1–b). Methods. A millimeter-wave room-temperature rotational spectrum of methyl ketene was recorded from 50 to 330 GHz. The internal rotation analysis of its ground state and first torsional excited state was performed with the rho-axis method employing the RAM36 program. Results. More than 3000 transitions of the rotational spectrum of the ground state (Kamax = 18) and first torsional excited state (Kamax = 13) of methyl ketene were fitted using a Hamiltonian that contains 41 parameters with a root mean square of 44 kHz. Column density limits were calculated but no lines were detected in the ISM belonging to methyl ketene.

scholarly journals A New Molecular Core in L1641

1987 ◽  
Vol 115 ◽  
pp. 81-82
Author(s):  
H. Takaba ◽  
Y. Fukui
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Hot Spots ◽  
Orion Nebula ◽  
Dark Cloud ◽  
Star Forming ◽  
Star Forming Regions ◽  
The North ◽  
Molecular Core ◽  
A Site

L1641 is a large dark cloud which extends 6.3 degree2 to the south of the Orion nebula (Lynds 1962). This region contains a reflection nebula, NGC 1999, several emission line stars and Herbig-Haro objects and is thought to be a site of on-going star formation. A CO(J = 1-0) map obtained with the Nagoya 1.5 m telescope (Takano 1983) revealed that CO hot spots extend further to the north by ∼ 30′ from NGC 1999. This suggests that L1641 may contain other regions of recent star formation. Therefore, we have mapped the L1641 cloud to investigate if there are other star-forming regions in it.

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