- ID:
- ivo://CDS.VizieR/J/ApJ/835/46
- Title:
- methoxy radical (CH_3_O) rotational spectrum
- Short Name:
- J/ApJ/835/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The methoxy radical (CH_3_O) has recently been detected in the interstellar medium and may be an important tracer of methanol-related chemistry in cold sources. Despite its importance, the spectral information needed to guide further astronomical searches is limited. We have therefore studied the low-temperature rotational spectrum in the laboratory within the spectral range of 246-303GHz. We have combined these new measurements with results from a number of literature reports to refine the molecular parameters and provide an updated and improved spectral line catalog. We present here the results of the laboratory studies and the refined analysis for the millimeter and submillimeter spectrum of methoxy.
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- ID:
- ivo://CDS.VizieR/J/ApJ/808/21
- Title:
- Methyl acetate (CH_3_COOCH_3_) rotational transitions
- Short Name:
- J/ApJ/808/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methyl acetate (CH_3_COOCH_3_) has been recently observed by the IRAM 30m radio telescope in Orion, though the presence of its deuterated isotopomers is yet to be confirmed. We therefore study the properties of various forms of methyl acetate, namely, CH_3_COOCH_3_, CH_2_DCOOCH_3_, and CH_3_COOCH_2_D. Our simulation reveals that these species could be produced efficiently in both gas and ice phases. Production of methyl acetate could follow radical-radical reaction between acetyl (CH_3_CO) and methoxy (CH_3_O) radicals. To predict abundances of CH_3_COOCH_3_ along with its two singly deuterated isotopomers and its two isomers (ethyl formate and hydroxyacetone), we prepare a gas-grain chemical network to study the chemical evolution of these molecules. Since gas-phase rate coefficients for methyl acetate and its related species are unknown, either we consider similar rate coefficients for similar types of reactions (by following existing databases) or we carry out quantum chemical calculations to estimate the unknown rate coefficients. For the surface reactions, we use adsorption energies of reactants from some earlier studies. Moreover, we perform quantum chemical calculations to obtain spectral properties of methyl acetate in infrared and sub-millimeter regions. We prepare two catalog files for the rotational transitions of CH_2_DCOOCH_3_ and CH_3_COOCH_2_D in JPL format, which could be useful for their detection in regions of interstellar media where CH_3_COOCH_3_ has already been observed.
- ID:
- ivo://CDS.VizieR/J/A+A/653/A116
- Title:
- Methylamine mid-IR spectra in ice mixtures
- Short Name:
- J/A+A/653/A116
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In the near future, high spatial and spectral infrared (IR) data of star-forming regions obtained by the James Webb Space Telescope (JWST) may reveal new solid-state features of various species, including more intriguing classes of chemical compounds. The identification of Complex organic molecules (COMs) in the upcoming data will only be possible when laboratory IR ice spectra of these species under astronomically relevant conditions are available for comparison. For this purpose, systematic series of laboratory measurements are performed, providing high-resolution IR spectra of COMs. Here, spectra of pure methylamine (CH_3_NH_2_) and methylamine-containing ices are discussed. The work is aimed at characterizing the mid-IR (500-4000cm^-1^, 20-2.5 microns) spectra of methylamine in pure and mixed ices to provide accurate spectroscopic data of vibrational bands that are most suited to trace this species in interstellar ices. Fourier transform infrared (FTIR) spectroscopy is used to record spectra of CH_3_NH_2_ in the pure form and mixed with H_2_O, CH_4_, and NH_3_, for temperatures ranging from 15 to 160K. The IR spectra in combination with HeNe laser (632.8nm) interference data of pure CH_3NH_2 ice was used to derive the IR band strengths of methylamine in pure and mixed ices. The refractive index of amorphous methylamine ice at 15K was determined as being 1.30+/-0.01. Accurate spectroscopic information and band strength values are systematically presented for a large set of methylamine-containing ices and different temperatures. Selected bands are characterized and their use as methylamine tracers is discussed. The selected bands include the following: the CH_3_ antisymmetric stretch band at 2881.3cm^-1^ (3.471 microns), the CH_3_ symmetric stretch band at 2791.9cm^-1^ (3.582 microns), the CH_3_ antisymmetric deformation bands, at 1455.0 and 1478.6cm^-1^ (6.873 microns and 6.761 microns), the CH_3 symmetric deformation band at 1420.3cm^-1^ (7.042 microns), and the CH_3_ rock at 1159.2cm^-1^ (8.621 microns). Using the laboratory data recorded in this work and ground-based spectra of ices toward YSOs (Young Stellar Objects), upper-limits for the methylamine ice abundances are derived. In some of these YSOs, the methylamine abundance is less than 4 percent relative to H_2_O.
- ID:
- ivo://CDS.VizieR/J/ApJS/215/25
- Title:
- Methyl formate (HCOOCH_3_) observations
- Short Name:
- J/ApJS/215/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed a sample of massive star-forming regions located over a range of distances from the Galactic center for methyl formate, HCOOCH_3_, and its isotopologues H^13^COOCH_3_ and HCOO^13^CH_3_. The observations were carried out with the APEX telescope in the frequency range 283.4-287.4GHz. Based on the APEX observations, we report tentative detections of the ^13^C-methyl formate isotopologue HCOO^13^CH_3_toward 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 1mm ALMA science verification observations of Orion-KL and confirm the detection of the ^13^C-methyl formate species in Orion-KL and image its spatial distribution. Our analysis shows that the ^12^C/^13^C isotope ratio in methyl formate toward the Orion-KL Compact Ridge and Hot Core-SW components (68.4+/-10.1 and 71.4+/-7.8, respectively) are, for both the ^13^C-methyl formate isotopologues, commensurate with the average ^12^C/^13^C ratio of CO derived toward Orion-KL. Likewise, regarding the other sources, our results are consistent with the ^12^C/^13^C in CO. We also report the spectroscopic characterization, which includes a complete partition function, of the complex H^13^COOCH_3_ and HCOO^13^CH_3_species. New spectroscopic data for both isotopomers H^13^COOCH_3_and HCOO^13^CH_3_, presented in this study, have made it possible to measure this fundamentally important isotope ratio in a large organic molecule for the first time.
- ID:
- ivo://CDS.VizieR/J/ApJS/207/26
- Title:
- MgH in the A^2^{Pi}-X^2^{Sigma}^+^ system
- Short Name:
- J/ApJS/207/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using laboratory hollow cathode spectra we have identified lines of the less common magnesium isotopologues of MgH, ^25^MgH and ^26^MgH, in the A^2^{Pi}-X^2^{Sigma}^+^ system. Based on the previous analysis of ^24^MgH, molecular lines have been measured and molecular constants derived for ^25^MgH and ^26^MgH. Term values and linelists, in both wavenumber and wavelength units, are presented. The A^2^{Pi}-X^2^{Sigma}^+^ system of MgH is important for measuring the magnesium isotope ratios in stars.
- ID:
- ivo://CDS.VizieR/J/A+A/597/A76
- Title:
- Mg-like ions energy levels
- Short Name:
- J/A+A/597/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations and relativistic configuration interaction (RCI) calculations were performed for states of the 3l3l', 3l4l' and 3s5l configurations in the Mg-like ions Ca IX - As XXII and Kr XXV. Valence and core-valence electron correlation effects are accounted for through large configuration state function expansions. Calculated excitation energies are in very good agreement with observations for the lowest levels. For higher lying levels observations are often missing and present energies aid line identification in spectra. Lifetimes and transition data are given for all ions. There is an excellent agreement for both lifetimes and transition data with recent multiconfiguration Hartree-Fock Breit Pauli calculations.
- ID:
- ivo://CDS.VizieR/J/A+A/574/A87
- Title:
- MgV lines collision rates for electron excitation
- Short Name:
- J/A+A/574/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transition probabilities and electron impact excitation collision strengths and rates for astrophysically important lines in Mg V are reported. The 86 fine-structure levels of the 2s^2^2p^4^, 2s2p^5^, 2p^6^, 2s2^2^p^3^3s, 2s^2^2p^3^3p and 2s^2^2p^3^3d configurations are included in our calculations. The effective collision strengths are presented as a function of electron temperature for solar and other astrophysical applications.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A82
- Title:
- Microwave spectra of CH3CHCCHCN
- Short Name:
- J/A+A/564/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A successful identification of an interstellar compound requires that its spectrum has first been assigned in the laboratory. New and sensitive radiotelescopes, such as ALMA, will make it possible to detect interstellar molecules in much smaller concentrations than before. Cyanoallene (CH_2_=C=CH-CN) has recently been observed in the dense molecular cloud TMC-1 by means of its rotational spectrum. Its methyl congener, 4-methylcyanoallene (CH_3_CH=C=CH-CN), may also be present in the interstellar medium (ISM). This chiral compound exists in two forms, which are mirror images. Chirality is an essential feature of life. So far, no chiral compounds have been detected in the ISM. The synthesis and assignment of the rotational spectrum of CH_3_CH=C=CH-CN, will facilitate the potential detection of this compound in the ISM.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A6
- Title:
- Microwave spectrum of 2-pentynenitrile (C2H5CCCN)
- Short Name:
- J/A+A/558/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New radiotelescopes, such as the very sensitive ALMA, will enable the detection of interstellar molecules in much lower concentrations than previously possible. A successful identification of an interstellar molecule requires that laboratory microwave and millimeter-wave spectra are investigated. Several cyanopolyynes and alkynylcarbonitriles have already been detected in the interstellar medium (ISM). Cyanoacetylene (HCCCN) is abundant in the ISM and its methyl derivative, 2-butynenitrile (CH3CCCN), is also present. The next derivative, ethyl cyanoacetylene, (2-pentynenitrile C_2_H_5_CCCN) may also be present in interstellar space. We report the rotational spectrum of the ethyl cyanoacetylene (C_2_H_5_CCCN). This is hoped to facilitate identifying gaseous ethyl cyanoacetylene in the ISM.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A43
- Title:
- Millimeter wave spectra of carbonyl cyanide
- Short Name:
- J/A+A/592/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- More than 30 cyanide derivatives of simple organic molecules have been detected in the interstellar medium, but only one dicarbonitrile has been found and that very recently. There is still a lack of high-resolution spectroscopic data particularly for dinitriles derivatives. The carbonyl cyanide molecule is a new and interesting candidate for astrophysical detection. It could be formed by the reaction of CO and CN radicals, or by substitution of the hydrogen atom by a cyano group in cyanoformaldehyde, HC(=O)CN, that has already been detected in the interstellar medium. The available data on the rotational spectrum of carbonyl cyanide is limited in terms of quantum number values and frequency range, and does not allow accurate extrapolation of the spectrum into the millimeter-wave range. To provide a firm basis for astrophysical detection of carbonyl cyanide we studied its millimeter-wave spectrum. Methods. The rotational spectrum of carbonyl cyanide was measured in the frequency range 152-308GHz and analyzed using Watson's A- and S-reduction Hamiltonians. The ground and first excited state of v5 vibrational mode were assigned and analyzed. More than 1100 distinct frequency lines of the ground state were fitted to produce an accurate set of rotational and centrifugal distortion constants up to the eighth order. The frequency predictions based on these constants should be accurate enough for astrophysical searches in the frequency range up to 500GHz and for transition involving energy levels with J<100 and Ka<42. Based on the results we searched for interstellar carbonyl cyanide in available observational data without success. Thus, we derived upper limits to its column density in different sources.
