- ID:
- ivo://CDS.VizieR/J/A+A/629/A72
- Title:
- Isotopic acetone laboratory rotational spectroscopy
- Short Name:
- J/A+A/629/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectra of minor isotopic species of molecules that are abundant in space may also be detectable. Their respective isotopic ratios may provide clues about the formation of these molecules. Emission lines of acetone in the hot molecular core Sagittarius B2(N2) are strong enough to warrant a search for its singly substituted 13C isotopologs. We want to study the rotational spectra of CH_3_^13^C(O)CH_3_ and ^13^CH_3_C(O)CH_3_ and search for them in Sagittarius B2(N2). We investigated the laboratory rotational spectrum of isotopically enriched CH_3_^13^C(O)CH_3_ between 40GHz and 910GHz and of acetone between 36GHz and 910GHz in order to study ^13^CH_3_C(O)CH_3_ in natural isotopic composition. In addition, we searched for emission lines produced by these species in a molecular line survey of Sagittarius B2(N) carried out with the Atacama Large Millimeter/submillimeter Array (ALMA). Discrepancies between predictions of the main isotopic species and the ALMA spectrum prompted us to revisit the rotational spectrum of this isotopolog. We assigned 9711 new transitions of CH_3_^13^C(O)CH_3_ and 63 new transitions of ^13^CH_3_C(O)CH_3_ in the laboratory spectra. More than 1000 additional lines were assigned for the main isotopic species.We modeled the ground state data of all three isotopologs satisfactorily with the ERHAM program. We find that models of the torsionally excited states {nu}_12_=1 and {nu}_17_=1 of CH_3_C(O)CH_3_ improve only marginally. No transition of CH_3_^13^C(O)CH_3_ is clearly detected toward the hot molecular core Sgr B2(N2). However, we report a tentative detection of ^13^CH_3_C(O)CH_3_ with a ^12^C/^13^C isotopic ratio of 27 that is consistent with the ratio previously measured for alcohols in this source. Several dozens of transitions of both torsional states of the main isotopolog are detected as well. Our predictions of CH_3_^13^C(O)CH_3_ and CH_3_C(O)CH_3_ are reliable into the terahertz region. The spectrum of ^13^CH_3_C(O)CH_3_ should be revisited in the laboratory with an enriched sample. The torsionally excited states v_12_=1 and v_17_=1 of CH_3_C(O)CH_3_ were not reproduced satisfactorily in our models. Nevertheless, transitions pertaining to both states could be identified unambiguously in Sagittarius B2(N2).
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/466/255
- Title:
- Isotopic ethyl cyanide
- Short Name:
- J/A+A/466/255
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Astronomical spectra of hot molecular clouds in the wavelength range from centimeter to submillimeter show a huge number of rotational lines due to the emission of complex organic molecules, and a large fraction of these lines are unidentified. The assignment of these unidentified lines to new molecules, to known molecules in excited states, or to their isotopologues requires a good knowledge of the spectroscopic parameters of these molecules. We present the experimental study of the spectroscopic properties of ^13^C-substituted ethyl cyanide ^13^CH3CH2CN, CH3^13^CH2CN, and CH3CH2^13^CN. The rotational spectra of the three species in the ground state have been measured in the frequency ranges from 5 to 26GHz using waveguide Fourier transform spectrometers and from 160 to 360GHz using a source-modulated spectrometer employing backward-wave oscillators (BWOs). A new accurate set of spectroscopic constants has been determined for each isotopic species. This permits prediction of the position of rotational lines that are best suited for detection with an accuracy of a few hundreds of kHz. The three isotopologues have been detected in an Orion IRc2 IRAM survey via several hundred of lines, illustrating that many "unidentified" bands are definitely due to isotopologues of known molecules.
- ID:
- ivo://CDS.VizieR/J/A+A/621/A143
- Title:
- Isotopic H_2_CS laboratory spectroscopic study
- Short Name:
- J/A+A/621/A143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Thioformaldehyde is an abundant molecule in various regions of the interstellar medium. However, available laboratory data limit the accuracies of calculated transition frequencies in the submillimeter region, in particular for minor isotopic species. We aim to determine spectroscopic parameters of isotopologs of H_2_CS that are accurate enough for predictions well into the submillimeter region.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A93
- Title:
- Isotopic H_2_NCN laboratory spectroscopic study
- Short Name:
- J/A+A/623/A93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cyanamide is one of the few interstellar molecules containing two chemically different N atoms. It was detected recently toward the solar-type protostar IRAS 16293-2422 B together with H_2_N^13^CN and HDNCN in the course of the Atacama Large Millemeter/submillimeter Array (ALMA) Protostellar Interferometric Line Survey (PILS). The detection of the 15N isotopomers or the determination of upper limits to their column densities was hampered by the lack of accurate laboratory data at the frequencies of the survey. We wanted to determine spectroscopic parameters of the ^15^N isotopomers of cyanamide that are accurate enough for predictions well into the submillimeter region and to search for them in the PILS data.
- ID:
- ivo://CDS.VizieR/J/ApJ/820/L26
- Title:
- J=1-0 transitions of argonium (ArH^+^)
- Short Name:
- J/ApJ/820/L26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent detections of ^36^ArH^+^ and ^38^ArH^+^ in the interstellar medium have triggered interest in argonium. This molecular cation has proved to be widespread in our galaxy in the diffuse medium and may serve as a very specific tracer of atomic gas and as a proxy for the cosmic-ray ionization rate. Pure rotational transitions of the two isotopologues detected in the ISM have never been recorded in the laboratory until this work. Here, we report on the first detection of the J=1<-0 transition of both ^36^ArH^+^ and ^38^ArH^+^ produced in a low-pressure glow discharge. All of the rotational and ro-vibrational transition frequencies available have been analyzed in global multi-isotopologues fit to give a comprehensive set of isotopic independent spectroscopic parameters. These data allow us to compute an improved set of rotational and ro-vibrational rest frequencies to assist astronomical searches of ArH^+^.
- ID:
- ivo://CDS.VizieR/J/ApJ/752/148
- Title:
- {kappa}-distributed electrons and OIII em. line
- Short Name:
- J/ApJ/752/148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The measurement of electron temperatures and metallicities in H II regions and planetary nebulae (PNe) has--for several decades--presented a problem: results obtained using different techniques disagree. What is worse, they disagree consistently. There have been numerous attempts to explain these discrepancies, but none has provided a satisfactory solution to the problem. In this paper, we explore the possibility that electrons in H II regions and PNe depart from a Maxwell-Boltzmann equilibrium energy distribution. We adopt a "{kappa}-distribution" for the electron energies. Such distributions are widely found in solar system plasmas, where they can be directly measured. This simple assumption is able to explain the temperature and metallicity discrepancies in H II regions and PNe arising from the different measurement techniques. We find that the energy distribution does not need to depart dramatically from an equilibrium distribution. From an examination of data from H II regions and PNe, it appears that {kappa}>~10 is sufficient to encompass nearly all objects. We argue that the kappa-distribution offers an important new insight into the physics of gaseous nebulae, both in the Milky Way and elsewhere, and one that promises significantly more accurate estimates of temperature and metallicity in these regions.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A66
- Title:
- Ketenimine (CH2CNH) submm rest-frequencies
- Short Name:
- J/A+A/565/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Imine compounds are thought to have a role in the interstellar formation of complex organic species, including pre-biotic molecules. Ketenimine (CH_2_CNH) is one of the four imines discovered in space. It was identified in Sgr B2(N-LMH) through the detection of three rotational lines in absorption. We present an extensive laboratory study of the ground-state rotational spectrum of CH_2_CNH at submillimetre wavelengths, aimed at obtaining accurate rest-frequencies for radio-astronomical searches. The investigation was carried out using a source-modulation microwave spectrometer equipped with a cell that is coupled to a pyrolysis apparatus working at 1000{deg}. The spectrum was recorded in the frequency range 80-620GHz with the detection of 150 transitions.
- ID:
- ivo://CDS.VizieR/J/A+A/589/A21
- Title:
- K-H_2_ line shapes for cool brown dwarfs spectra
- Short Name:
- J/A+A/589/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of cooler and cooler brown dwarfs show that the contribution from broadening at many bars pressure is becoming important. The opacity in the red optical to near-IR region under these conditions is dominated by the extremely pressure-broadened wings of the alkali resonance lines, in particular, the KI resonance doublet at 0.77um. Collisions with H_2_ are preponderant in brown dwarf atmospheres at an effective temperature of about 1000K; the H_2_ perturber densities reach several 10^19^ even in Jupiter-mass planets and exceed 10^20^ for super-Jupiters and older Y dwarfs. As a consequence, it appears that when the far wing absorption due to alkali atoms in a dense H_2_ atmosphere is significant, accurate pressure broadened profiles that are valid at high densities of H_2_ should be incorporated into spectral models.
- ID:
- ivo://CDS.VizieR/VI/153
- Title:
- K-shell photoabsorption and photoionization
- Short Name:
- VI/153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the final report of a three-paper series on the K-shell photoabsorption and photoionization of trace elements (low cosmic abundance), namely F, Na, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu, and Zn. K lines and edges from such elements are observed in the X-ray spectra of supernova remnants, galaxy clusters, and accreting black holes and neutron stars, their diagnostic potential being limited by poor atomic data. We here complete the previously reported radiative datasets with new photoabsorption and photoionization cross sections for isoelectronic sequences with electron number 19<=N<=26. We also describe the access to and integrity and usability of the whole resulting atomic database. Target representations were obtained with the atomic structure code AUTOSTRUCTURE. Where possible, cross sections for ground-configuration states were computed with the Breit--Pauli R-matrix method (BPRM) in either intermediate or LS coupling including damping (radiative and Auger) effects; otherwise and more generally, they were generated in the isolated-resonance approximation with AUTOSTRUCTURE. Cross sections were computed with BPRM only for the K (N=19) and Ca (N=20) isoelectronic sequences, the latter in LS coupling. For the remaining sequences (21<=N<=26), AUTOSTRUCTURE was run in LS-coupling mode taking into account damping effects. Comparisons between these two methods for K-like ZnXII and Ca-like ZnXI show that to ensure reasonable accuracy, the LS calculations must be performed taking into account the non-fine-structure relativistic corrections. The original data structures of the BPRM and AUTOSTRUCTURE output files, namely photoabsorption and total and partial photoionization cross sections, are maintained but supplemented with files detailing the target (N_T_-electron system, where N_T_=N-1) representations and photon states (N-electron system). We conclude that because of the large target size, the photoionization of ions with N>20 involving inner-shell excitations rapidly leads to untractable BPRM calculations, and is then more effectively treated in the isolated resonance approximation with AUTOSTRUCTURE. This latter approximation by no means involves small calculations as Auger damping must be explicitly specified in the intricate decay routes.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A121
- Title:
- Lab measurements for C-cyanomethanimine
- Short Name:
- J/A+A/609/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- C-cyanomethanimine (HNCHCN), existing in the two Z and E isomeric forms, is a key prebiotic molecule, but, so far, only the E isomer has been detected towards the massive star forming region Sagittarius B2(N) using transitions in the radio wavelength domain. With the aim of detecting HNCHCN in Sun-like star-forming regions, the laboratory investigation of its rotational spectrum has been extended to the milllimeter-/submillimeter-wave (mm-/submm-) spectral window where several unbiased spectral surveys have been already obtained. High-resolution laboratory measurements of the rotational spectrum of C-cyanomethanimine were carried out in the 100-420GHz range using a frequency-modulation absorption spectrometer. The C-cyanomethanimine spectral features were then searched for in the mm-wave range using the high-sensitivity and unbiased spectral surveys obtained with the IRAM 30-m antenna in the ASAI context, the earliest stages of star formation from starless to evolved Class I objects being sampled. For both the Z and E isomers, the spectroscopic work has led to an improved and extended knowledge of the spectroscopic parameters, thus providing accurate predictions of the rotational signatures up to ~700GHz. So far, no C-cyanomethanimine emission has been detected towards the ASAI targets, and upper limits on the column density of 10^11^-10^12^cm^-2^ could only be derived. Consequently, the C-cyanomethanimine abundances have to be less than a few 10^-10^ for starless and hot-corinos. A less stringent constraint, <=10^-9^, is obtained for shocks sites. The combination of the upper limits on the abundances of C-cyanomethanimine together with accurate laboratory frequencies up to ~700GHz poses the basis for future higher sensitivity searches around Sun-like star forming regions. For compact (typically less than 1 arcsec) and chemically enriched sources such as hot-corinos, the use of interferometers as NOEMA and ALMA in their extended configurations are clearly needed.
