- 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.
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Search Results
- 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/ApJ/832/42
- Title:
- Rotational spectrum of vinyl formate (CH_2_=CHOCHO)
- Short Name:
- J/ApJ/832/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous detections of methyl and ethyl formate make other small substituted formates potential candidates for observation in the interstellar medium. Among them, vinyl formate is one of the simplest unsaturated carboxylic ester. The aim of this work is to provide direct experimental frequencies of the ground vibrational state of vinyl formate in a large spectral range for astrophysical use. The room-temperature rotational spectrum of vinyl formate has been measured from 80 to 360GHz and analyzed in terms of Watson's semirigid rotor Hamiltonian. Two thousand six hundred transitions within J=3-88 and K_a_=0-28 were assigned to the most stable conformer of vinyl formate and a new set of spectroscopic constants was accurately determined. Spectral features of vinyl formate were then searched for in Orion KL, Sgr B2(N), B1-b, and TMC-1 molecular clouds. Upper limits to the column density of vinyl formate are provided.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A3
- Title:
- rotational transitions of cyanoacetamide
- Short Name:
- J/A+A/644/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cyanoacetamide is a branched chain -CN bearing molecule which is also an amide derivative target molecule in the interstellar medium. The aim of our investigation is to analyze the feasibility of a plausible formation process of protonated cyanoacetamide under interstellar conditions and to provide direct experimental frequencies of the ground vibrational state of the neutral form in the microwave region in order to enable its eventual identification in the interstellar medium. We used high-level theoretical computations to study the formation process of protonated cyanoacetamide. Furthermore, we employed a high resolution laser ablation molecular beam Fourier transform (LA-MB-FTMW) spectroscopic technique to measure the frequencies of the neutral form. We report the first rotational characterization of cyanoacetamide and a precise set of the relevant rotational spectroscopic constants have been determined as a first step to identify the molecule in the interstellar medium. We performed full exploration of the Potential Energy Surface (PES) to study a gas-phase reaction on the formation process of protonated cyanoacetamide. We found an exothermic process with no net activation barrier initiated by the high-energy isomer of protonated hydroxylamine, which leads to protonated cyanoacetamide.
- ID:
- ivo://CDS.VizieR/J/ApJS/169/28
- Title:
- Rotational transitions of Methyl carbamate
- Short Name:
- J/ApJS/169/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rotational-torsional spectrum of the syn conformer of methyl carbamate [CH_3_OC(:O)NH_2_], an isomer of the essential amino acid glycine [NH_2_CH_2_C(:O)OH], has been recorded at room temperature in the spectral region from 79 to 371GHz. Methyl carbamate possesses a methyl group internal rotor, which gives rise to A and E torsional substates, and associated splittings in the rotational spectrum. Almost 6000 new rotational transitions arising from the vibrational ground state have been assigned, about half of them belonging to the E torsional substate. The Fast Scan Submillimeter-wave Spectroscopic Technique (FASSST) spectrometer at the Ohio State University was used for the present measurements
- ID:
- ivo://CDS.VizieR/J/A+AS/117/561
- Title:
- Rovibrational dipole matrix elements for CO
- Short Name:
- J/A+AS/117/561
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Expansion coefficients of the polynomial expansion representing the transition D-values for the {DELTA}v=1 band and the ^12^C^16^O isotope. Results are obtained using the Electric Dipole Moment Function EDMF2 (Langhoff & Bauschlicher 1995, J. Chem. Phys. 102, 5220). The fits are better than 1% when |m|<=m_max_.
- ID:
- ivo://CDS.VizieR/J/ApJ/783/L5
- Title:
- Ro-vibration transitions of the protonated argon ion
- Short Name:
- J/ApJ/783/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The protonated argon ion, ^36^ArH^+^, was recently identified in the Crab Nebula from Herschel spectra. Given the atmospheric opacity at the frequency of its J=1-0 and J=2-1 rotational transitions (617.5 and 1234.6GHz, respectively), and the current lack of appropriate space observatories after the recent end of the Herschel mission, future studies on this molecule will rely on mid-infrared observations. We report on accurate wavenumber measurements of ^36^ArH^+^ and ^38^ArH^+^ rotation-vibration transitions in the v=1-0 band in the range 4.1-3.7{mu}m (2450-2715/cm). The wavenumbers of the R(0) transitions of the v=1-0 band are 2612.50135+/-0.00033 and 2610.70177+/-0.00042/cm(+/-3{sigma}) for ^36^ArH^+^ and ^38^ArH^+^, respectively. The calculated opacity for a gas thermalized at a temperature of 100K and with a linewidth of 1km/s of the R(0) line is 1.6x10^-15^xN(^36^ArH^+^). For column densities of ^36^ArH^+^ larger than 1x10^13^/cm^2^, significant absorption by the R(0) line can be expected against bright mid-IR sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/76
- Title:
- r-process peaks elements in HD 160617
- Short Name:
- J/ApJ/750/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first detection of elements at all three r-process peaks in the metal-poor halo star HD 160617. These elements include arsenic and selenium, which have not been detected previously in halo stars, and the elements tellurium, osmium, iridium, and platinum, which have been detected previously. Absorption lines of these elements are found in archive observations made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We present up-to-date absolute atomic transition probabilities and complete line component patterns for these elements. Additional archival spectra of this star from several ground-based instruments allow us to derive abundances or upper limits of 45 elements in HD 160617, including 27 elements produced by neutron-capture reactions. The average abundances of the elements at the three r-process peaks are similar to the predicted solar system r-process residuals when scaled to the abundances in the rare earth element domain. This result for arsenic and selenium may be surprising in light of predictions that the production of the lightest r-process elements generally should be decoupled from the heavier r-process elements.
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/2461
- Title:
- ScII effective collision strengths
- Short Name:
- J/MNRAS/424/2461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate fine-structure atomic data for the Fe-peak elements are essential for interpreting astronomical spectra. There is a severe paucity of data available for ScII, highlighted by the fact that no collision strengths are readily available for this ion. We present electron-impact excitation collision strengths and Maxwellian averaged effective collision strengths for ScII. The collision strengths were calculated for all 3916 transitions amongst 89 jj levels (arising from the 3d4s, 3d^2^, 4s^2^, 3d4p, 4s4p, 3d5s, 3d4d, 3d5p, 4p^2^ and 3d4f configurations), resulting in a 944 coupled channel problem. The R-matrix package RMATRXII was utilized, along with the transformation code fine and the external region code pstgf, to calculate the collision strengths for a range of incident electron energies in the 0 to 8.3 Rydberg region. Maxwellian averaged effective collision strengths were then produced for 27 temperatures lying within the astrophysically significant range of 30 to 105K.
