- ID:
- ivo://CDS.VizieR/J/ApJS/229/26
- Title:
- Rotational spectra of aminoacetonitrile
- Short Name:
- J/ApJS/229/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a detailed spectroscopic investigation of the interstellar aminoacetonitrile, a possible precursor molecule of glycine. Using a combination of Stark and frequency-modulation microwave and millimeter wave spectroscopies, we observed and analyzed the room-temperature rotational spectra of 29 excited states with energies up to 1000cm^-1^. We also observed the ^13^C isotopologues in the ground vibrational state in natural abundance (1.1%). The extensive data set of more than 2000 new rotational transitions will support further identifications of aminoacetonitrile in the interstellar medium.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/662/1309
- Title:
- Rotational spectra of small PAHs
- Short Name:
- J/ApJ/662/1309
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Pure rotational spectra of four small polycyclic aromatic hydrocarbons have been observed by Fourier transform microwave spectroscopy of a molecular beam in the frequency range from 7 to 37GHz. Initial searches for acenaphthene (C_12_H_10_), acenaphthylene (C_12_H_8_), and fluorene (C_13_H_10_) were guided by quantum chemical calculations performed at the B3LYP/cc-pVTZ level of theory. All three molecules exhibit b-type rotational spectra and are calculated to be moderately polar, with dipole moments of 0.3-0.9D. Close agreement (to better than 1%) between the calculated equilibrium and experimentally derived ground-state rotational constants is achieved. Selected transitions of acenaphthene and fluorene have also been measured in the 3mm region by conventional free-space absorption spectroscopy, as have transitions of the previously studied azulene (C_10_H_8_). The data presented here facilitate deep radio astronomical searches with large radio telescopes.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A75
- Title:
- Rotational spectroscopy and ISM search CPCA
- Short Name:
- J/A+A/645/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At least a dozen molecules with a formyl group (HCO) have been observed to ate in the interstellar medium (ISM), suggesting that other such species exist nd await discovered. However there is still a lack of high-resolution spectroscopic data for simple molecular species of this type that could provide basis for their detection. Cyclopropanecarboxaldehyde, c-C_3_H_5_CHO, is a small molecule containing a formyl group and is an interesting candidate for astrophysical detection. The rotational spectrum of cyclopropanecarboxaldehyde has been observed before, but its experimental rotational parameters are not precise enough to allow its detection in the ISM. We measured the rotational spectrum of cyclopropanecarboxaldehyde in the frequency ranges 31.5-50GHz and 72-116.5GHz using the GACELA (GAS CEll for Laboratory Astrophysics) broadband high resolution rotational spectrometer constructed at the Yebes Observatory. The spectroscopic study was supported by high-level theoretical calculations which were used in the identification of the vibrational excited states of cyclopropanecarboxaldehyde. The analysis of the rotational spectrum of cyclopropanecarboxaldehyde allowed us to obtain accurate rotational parameters for the ground state of both cis and trans isomers, which were used to derive predictions sufficiently reliable up to 500GHz. In addition to the ground states, we identified twelve and six vibrationally excited states for the trans and cis isomers, respectively, including fundamental modes, multiple excitation quanta and combination states. We found that the gas phase concentration of the trans isomer is almost 1.2 times larger than that for the cis one. The new experimental rotational parameters were employed to search for cyclopropanecarboxaldehyde in the warm molecular clouds Orion KL and Sgr B2(N) using the spectral surveys captured by ALMA (Orion) and IRAM 30m (Sgr) at 1mm and 3mm, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A82
- Title:
- Rotational spectroscopy of diisocyanomethane
- Short Name:
- J/A+A/544/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Several organic isocyanides have been observed so far in ISM (HNC, CH_3_NC, HCCNC). However there is still a lack of high-resolution spectroscopic data on simple iso- cyanides that could provide a basis for their detection. Diisocyanomethane (NC-CH_2_-CN) is a small molecule having only 7 atoms and being an interesting candidate for astrophysical detection. Rotational spectrum of diisocyanomethane has never been studied before. We measured the rotational spectrum of diisocyanomethane in the frequency range 120-620GHz using Lille fast-scan and solid-state source spectrometers. The spectroscopic study was supported by high-level theoretical calculations on molecular structure and both harmonic and anharmonic force field. The ground and the first excited vibrational state (v15) were assigned and analyzed. The dataset is composed of more than 2000 measured and fitted lines allows accurate predictions of transition frequencies of diisocyanomethane in the range up to 900GHz. The statistical analysis of the results of the fit shows that the use of S-reduction of Watson rovibrational Hamiltonian for spectral modelling is more appropriate.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A53
- Title:
- Rotational spectroscopy of imidazole
- Short Name:
- J/A+A/628/A53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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. 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 1mm wavelength regime. The rotational spectrum of imidazole was recorded in selected frequency regions from 2 to 295GHz. 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). 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 SgrB2(N2). Its non-detection implies that it is at least 3400 times less abundant than ethyl cyanide in this source. 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.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A73
- Title:
- Rotational spectroscopy of methyl mercaptan
- Short Name:
- J/A+A/629/A73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new global study of the millimeter wave, submillimeter wave, and THz spectra of the lowest three torsional states of methyl mercaptan (CH_3_SH). New measurements have been carried out between 50 and 510GHz using the Kharkiv mm wave and the Cologne submm wave spectrometers whereas THz spectra records were used from our previous study. The new data involving torsion-rotation transitions with J up to 61 and Ka up to 18 were combined with previously published measurements and fitted using the rho-axis-method torsion-rotation Hamiltonian. The final fit used 124 parameters to give an overall weighted root- mean-square deviation of 0.72 for the dataset consisting of 6965 microwave and 16345 FIR line frequencies sampling transitions within and between the ground, first, and second excited torsional states of the molecule. This investigation presents a twofold expansion in the J quantum numbers and a significant improvement in the fit quality, especially for the microwave part of the data thus allowing us to provide improved predictions to support astronomical observations.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A152
- Title:
- Rotational spectrum of ^13^C methylamine
- Short Name:
- J/A+A/587/A152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methylamine (CH_3_NH_2_) is a light molecule of astrophysical interest, which has an intensive rotational spectrum that extends in the submillimeter wave range and far beyond, even at temperatures characteristic for the interstellar medium. It is likely for ^13^C isotopologue of methylamine to be identified in astronomical surveys, but there is no information available for the ^13^CH_3_NH_2_ millimeter and submillimeter wave spectra. In this context, to provide reliable predictions of ^13^CH_3_NH_2_ spectrum in millimeter and submillimeter wave ranges, we have studied rotational spectra of the 13C methylamine isotopologue in the frequency range from 48 to 945GHz. The spectrum of ^13^C methylamine was recorded using conventional absorption spectrometers in Lille and Kharkov. The analysis of the rotational spectrum of ^13^C methylamine in the ground vibrational state was performed on the basis of the group- theoretical high-barrier tunneling Hamiltonian that was developed for methylamine by Ohashi and Hougen. The available multiple observations of the parent methylamine species toward Sgr B2(N) at 1, 2, and 3mm using the Submillimeter Telescope and the 12 m antenna of the Arizona Radio Observatory were used to make a search for interstellar ^13^CH_3_NH_2_. In the recorded spectra, we have assigned 2721 rotational transitions that belong to the ground vibrational state of the ^13^CH_3_NH_2_. These measurements were fitted to the Hamiltonian model that uses 75 parameters to achieve an overall weighted rms deviation of 0.73. On the basis of these spectroscopic results, predictions of transition frequencies in the frequency range up to 950GHz with J<50 and Ka<20 are presented. The search for interstellar ^13^C methylamine in available observational data was not successful and therefore only an upper limit of 6.5x10^14^cm^-2^ can be derived for the column density of ^13^CH_3_NH_2_ toward Sgr B2(N), assuming the same source size, temperature, linewidth, and systemic velocity as for parent methylamine isotopic species.
- ID:
- ivo://CDS.VizieR/J/A+A/500/1109
- Title:
- Rotational spectrum of HCOO^13^CH_3_
- Short Name:
- J/A+A/500/1109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Laboratory measurements and analysis of the microwave and millimeter-wave spectra of potential interstellar molecules are a prerequisite for their subsequent identification by radioastronomical techniques. The spectral analysis provides spectroscopic parameters that are used in the assignment procedure of the laboratory spectra, and that also predict the frequencies of transitions not measured in the laboratory with a high degree of precision. An experimental laboratory study and its theoretical analysis is presented for ^13^C_2_-methyl formate (HCOO^13^CH_3_) allowing a search for this isotopologue in the Orion molecular cloud. The ^13^C_1_-methyl formate (H^13^COOCH_3_) molecule was also searched for in this interstellar cloud, using previously published spectroscopic data.
- ID:
- ivo://CDS.VizieR/J/ApJS/190/315
- Title:
- Rotational spectrum of H^13^COOCH_3_
- Short Name:
- J/ApJS/190/315
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A compilation of the available spectroscopic millimeter- and submillimeter-wave data of the ground and first excited states of ^13^C_1_-methyl formate (H^13^COOCH_3_) has been carried out. The exhaustive analysis of the available transition lines of H^13^COOCH_3_ has led to the assignment of 7457 spectral lines by means of a global fit of 45 parameters, using the Rho-Axis Method (RAM) and the BELGI-Cs code, with a resulting unitless standard deviation of 0.57. Over 1600 lines are included for the first time in the fit. In addition, the line strengths of spectral lines are also calculated using the most recent experimental measurement of the electric dipole moment. In conclusion, the present study represents a notable improvement with respect to previous H^13^COOCH_3_ spectral analyses. Therefore, the better accuracy of the present analysis may help the future identification of new H^13^COOCH_3_ lines in the interstellar and circumstellar media, and may contribute to decrease some of the spectral confusion due to these species in astronomical surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A44
- Title:
- Rotational spectrum of MAAN (CH_2_NCH_2_CN)
- Short Name:
- J/A+A/559/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aminoacetonitrile has been detected in the interstellar medium and the Strecker-type synthesis is considered as one of its possible mechanisms of formation in this medium. Methyleneaminoacetonitrile (CH_2_=N-CH_2_-CN, MAAN) is one of the by-products of the Strecker reaction and a good candidate for astrophysical detection. Rotational spectrum of MAAN has never been studied before. To provide the basis for the detection of MAAN in the interstellar medium we studied its millimeter and submillimeter-wave spectrum. The rotational spectrum of MAAN was measured in the frequency range 120-600GHz. The spectroscopic study was supported by theoretical calculations of the molecular structure and harmonic force field. The ground and two lowest excited vibrational states of the most stable synperiplanar conformation of MAAN were assigned and analyzed. Obtained sets of rotational constants allows us to make accurate predictions of transition frequencies of MAAN in the frequency range up to 900GHz.
