- ID:
- ivo://CDS.VizieR/J/A+A/538/A51
- Title:
- Rotational spectrum of CH_3_CH(NH_2_)CN
- Short Name:
- J/A+A/538/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- No chiral molecule has been detected in the interstellar medium (ISM) so far. A good candidate for an interstellar detection is 2-aminopropionitrile (CH_3_CH(NH_2_)CN), a chiral and the simplest molecule with a C_3_H_6_N_2_ formula. The first member of this series, aminoacetonitrile (H_2_NCH_2_CN), was recently detected, demonstrating that at least one aminonitrile exist in the ISM. Experimental spectra of 2-aminopropionitrile have been recorded in the microwave and sub-mm energy range (8-80GHz, 150-660GHz). An unbiased spectral survey of the 80-116GHz atmospheric window performed with the IRAM 30m telescope is used to search for this molecule in the hot core Sgr B2(N). This survey is analysed in the local thermodynamical equilibrium (LTE) approximation. The emission of 2-aminopropionitrile is modeled simultaneously with the emission of all molecules known in Sgr B2(N), which allows to properly take into account line blending and avoid mis-assignments. Only 10 groups of transitions of 2-aminopropionitrile are not severely affected by line blending in the Sgr B2(N) spectrum. Six of them could be considered as tentatively detected but the LTE predictions of the four remaining groups are not (or only marginally) consistent with the observed spectrum. Therefore, only an upper limit of 1.7*10^16^cm^-2^ can be securely derived for the column density of 2-aminopropionitrile toward Sgr B2(N).
Number of results to display per page
Search Results
- 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/616/A173
- Title:
- Rotational spectrum of ethyl isocyanate
- Short Name:
- J/A+A/616/A173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Relatively high abundances of methyl isocyanate (CH_3_NCO), a methyl derivative of isocyanic acid (HNCO), found in the Orion KL and Sgr B2 molecular clouds suggest that its ethyl derivative, ethyl isocyanate (CH_3_CH_2_NCO), may also be present. 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. The rotational spectrum of ethyl isocyanate was recorded at room temperature from 80 to 340GHz using the millimeter wave spectrometer in Valladolid. Assigned rotational transitions were analyzed using the S-reduced semirigid-rotor Hamiltonian. 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-energy 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 CH_3_CH_2_NCO in these high-mass star-forming regions were obtained.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A67
- Title:
- Rotational spectrum of methoxyacetaldehyde
- Short Name:
- J/A+A/619/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methoxyacetaldehyde belongs to a group of structural isomers with the general formula C_3_H_6_O_2_, of which methyl acetate and ethyl formate are known interstellar molecules. Rotational data available for methoxyacetaldehyde are limited to 40GHz, which makes predictions at higher frequencies rather uncertain. 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. The rotational spectrum of methoxyacetaldehyde was recorded at room-temperature from 75 to 120GHz and from 170 to 310GHz using the millimeter-wave spectrometer in Valladolid. Additional measurements were also performed at conditions of supersonic expansion from 6 to 18GHz. The assigned rotational transitions were analyzed using the S-reduced semirigid-rotor Hamiltonian. 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.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A24
- Title:
- Rotational spectrum of methoxyamine
- Short Name:
- J/A+A/609/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methoxyamine is a potential interstellar amine that has been predicted by gas-grain chemical models for the formation of complex molecules. The aim of this work is to provide direct experimental frequencies of its ground-vibrational state in the millimeter and submillimeter-wave regions to achieve its detection in the interstellar medium. Methoxyamine was chemically liberated from its hydrochloride salt, and its rotational spectrum was recorded at room temperature from 75 to 480GHz using the millimeter-wave spectrometer in Valladolid. Many observed transitions revealed A-E splitting caused by the internal rotation of the methyl group, which had to be treated with specific internal rotation codes. Over 400 lines were newly assigned for the most stable conformer of methoxyamine, and a precise set of spectroscopic constants was obtained. Spectral features of methoxyamine were then searched for in the Orion KL, Sgr B2, B1-b, and TMC-1 molecular clouds. Upper limits to the column density of methoxyamine were derived.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A55
- Title:
- Rotational spectrum of propiolamide
- Short Name:
- J/A+A/647/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For all the amides detected in the interstellar medium (ISM), the corresponding nitriles or isonitriles have also been detected in the ISM, some of which have relatively high abundances. Among the abundant nitriles for which the corresponding amide has not yet been detected is cyanoacetylene (HCCCN), whose amide counterpart is propiolamide (HCCC(O)NH_2_). With the aim of supporting searches for this amide in the ISM, we provide a complete rotational study of propiolamide from 6GHz to 440GHz. Time-domain Fourier transform microwave (FTMW) spectroscopy under supersonic expansion conditions between 6GHz and 18GHz was used to accurately measure and analyze ground-state rotational transitions with resolved hyperfine structure arising from nuclear quadrupole coupling interactions of the 14N nucleus. We combined this technique with the frequency-domain roomtemperature millimeter wave and submillimeter wave spectroscopies from 75GHz to 440GHz in order to record and assign the rotational spectrain the ground state and in the low-lying excited vibrational states. We used the ReMoCA spectral line survey performed with the Atacama Large Millimeter/submillimeter Array toward the star-forming region Sgr B2(N) to search for propiolamide. We identified and measured more than 5500 distinct frequency lines of propiolamide in the laboratory. These lines were fitted using an effective semi-rigid rotor Hamiltonian with nuclear quadrupole coupling interactions taken into consideration. We obtained accurate sets of spectroscopic parameters for the ground state and the three low-lying excited vibrational states. We report the nondetection of propiolamide toward the hot cores Sgr B2(N1S) and Sgr B2(N2). We find that propiolamide is at least 50 and 13 times less abundant than acetamide in Sgr B2(N1S) and Sgr B2(N2), respectively, indicating that the abundance difference between both amides is more pronounced by at least a factor of 8 and 2, respectively, than for their corresponding nitriles. Although propiolamide has yet to be included in astrochemical modeling networks, the observed upper limit to the ratio of propiolamide to acetamide seems consistent with the ratios of related species as determined from past simulations. The comprehensive spectroscopic data presented in this paper will aid future astronomical searches.
- ID:
- ivo://CDS.VizieR/J/ApJS/205/9
- Title:
- Rotational transition frequencies of HCOOCH_3_
- Short Name:
- J/ApJS/205/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The cis-methyl formate molecule (HCOOCH_3_) is a well known molecule found in interstellar space. Recently, rotational lines of methyl formate in the first CH_3_ torsional excited state were observed in Orion KL and W51e2. It is quite natural to observe methyl formate in even higher vibrational states considering the temperature estimated in Orion KL and W51e2. Maeda et al. (2008JMoSp.251..293M) reported results on the laboratory spectroscopy of methyl formate including the spectral analysis in its second CH_3_ torsional state. Their assignments were limited to a series of a-type R-branch lines and low K_a_ b-type R-branch transitions, and many assigned lines are excluded in the least-squares analysis. In the present study, we extended the line assignments of both the A- and E-species transitions in the second CH_3_ torsional state especially in the frequency region below the 120GHz region. By combining the present assignments and those made by Maeda et al., 1951 transitions in total for the second CH_3_ torsional state, 1096 A-species transitions up to J=39, and K_a_=15 and 855 E-species transitions up to J=35 and K_a_=13, were least-squares analyzed by using the pseudo-principal-axis-method Hamiltonian with 42 parameters consisting of rotational, centrifugal distortion, and internal rotational constants in the second CH_3_ torsional state. In addition, 1012 transitions out of 1096 A-species transitions could also be least-squares analyzed by using Watson's A-reduced Hamiltonian with 43 parameters, which can serve to calculate the energy levels of the A-species lines of molecules with the CH_3_ internal rotation conveniently.
