- ID:
- ivo://CDS.VizieR/J/A+A/602/A34
- Title:
- HOCO+ and DOCO+ rest frequencies
- Short Name:
- J/A+A/602/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HOCO^+^ is a polar molecule that represents a useful proxy for its parent molecule CO2, which is not directly observable in the cold interstellar medium. This cation has been detected towards several lines of sight, including massive star forming regions, protostars, and cold cores. Despite the obvious astrochemical relevance, protonated CO2 and its deuterated variant, DOCO^+^, still lack an accurate spectroscopic characterisation. The aim of this work is to extend the study of the ground-state pure rotational spectra of HOCO^+^ and DOCO^+^ well into the sub-millimetre region. Ground-state transitions have been recorded in the laboratory using a frequency-modulation absorption spectrometer equipped with a free-space glow-discharge cell. The ions were produced in a low-density, magnetically confined plasma generated in a suitable gas mixture. The ground-state spectra of HOCO^+^ and DOCO^+^ have been investigated in the 213-967GHz frequency range; 94 new rotational transitions have been detected. Additionally, 46 line positions taken from the literature have been accurately remeasured. The newly measured lines have significantly enlarged the available data sets for HOCO^+^ and DOCO^+^, thus enabling the determination of highly accurate rotational and centrifugal distortion parameters. Our analysis shows that all HOCO^+^ lines with Ka>=3 are perturbed by a ro-vibrational interaction that couples the ground state with the v5=1 vibrationally excited state. This resonance has been explicitly treated in the analysis in order to obtain molecular constants with clear physical meaning. The improved sets of spectroscopic parameters provide enhanced lists of very accurate sub-millimetre rest frequencies of HOCO^+^ and DOCO
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/216/3
- Title:
- H_2_O:He collisions between 20-120K
- Short Name:
- J/ApJS/216/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- State-to-state rate coefficients for ortho-H_2_O:He and para-H_2_O:He inelastic collisions in the 20-120K thermal range are investigated by means of an improved experimental procedure. This procedure is based on the use of a kinetic master equation (MEQ) which describes the evolution of populations of H_2_O rotational levels along a supersonic jet of H_2_O highly diluted in helium. The MEQ is expressed in terms of experimental observables and rate coefficients for H_2_O:He inelastic collisions. The primary experimental observables are the local number density and the populations of the rotational energy levels of H_2_O, quantities which are determined along the jet with unprecedented accuracy by means of Raman spectroscopy with high space resolution. Sets of rate coefficients from the literature and from present close-coupling calculations using two different potential energy surfaces (PESs) have been tested against the experiment. The Green et al. (VI/59) rate coefficients are up to 50% too low compared to the experiment, while most rates calculated here from the Hodges et al. (2002JChPh.116.1397H) PES and the Patkowski et al. (2002, JMoSt TEOCHEM, 591, 231) PES are much closer to the experimental values. Experimental rates with an estimated accuracy on the order of 10% have been obtained for ortho-H_2_O:He and para-H_2_O:He inelastic collisions between 20 and 120K by scaling and averaging the theoretical rates to the experiment.
- ID:
- ivo://CDS.VizieR/J/MNRAS/406/1745
- Title:
- H2O in interstellar shock waves
- Short Name:
- J/MNRAS/406/1745
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The dissipation of kinetic energy that occurs in interstellar shock waves is accompanied by the emission of radiation. In the case of shocks that are propagating into mainly molecular gas, the emission occurs principally in lines of the species H_2_, H, O, CO and H_2_O. The relative intensities of these emission lines are indicative of the type and speed of the shock wave and of the physical conditions in the ambient gas. We present the results of computations of the intensities of these lines, for small grids of models of C- and J-type shock waves, and compare with the results of previous calculations. Our results should serve to aid the interpretation of observations made with the Herschel and other satellites.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A160
- Title:
- Hot aminoacetonitrile in Sgr B2
- Short Name:
- J/A+A/641/A160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aminoacetonitrile, a molecule detected in the interstellar medium only towards the star-forming region Sagittarius B2 (Sgr B2) thus far, is considered an important prebiotic species; in particular it is a possible precursor of the simplest amino acid glycine. To date, observations were limited to ground state emission lines, whereas transitions from within vibrationally excited states remained undetected. We wanted to accurately determine the energies of the low-lying vibrational states of aminoacetonitrile, which are expected to be populated in Sgr B2(N1), the main hot core of Sgr B2(N). This step is fundamental in order to properly evaluate the vibration-rotation partition function of aminoacetonitrile as well as the line strengths of the rotational transitions of its vibrationally excited states. This is necessary to derive accurate column densities and secure the identification of these transitions in astronomical spectra. The far-infrared ro-vibrational spectrum of aminoacetonitrile has been recorded in absorption against a synchrotron source of continuum emission. Three bands, corresponding to the lowest vibrational modes of aminoacetonitrile, were observed in the frequency region below 500cm^-1^. The combined analysis of ro-vibrational and pure rotational data allowed us to prepare new spectral line catalogs for all the states under investigation. We used the imaging spectral line survey ReMoCA performed with ALMA to search for vibrationally excited aminoacetonitrile toward Sgr B2(N1). The astronomical spectra were analyzed under the local thermodynamic equilibrium (LTE) approximation. Almost 11000 lines have been assigned during the analysis of the laboratory spectrum of aminoacetonitrile, thanks to which the vibrational energies of the v_11_=1, v_18_=1, and v_17_=1 states have been determined. The whole dataset, which includes high J and Ka transitions, is well reproduced within the experimental accuracy. Reliable spectral predictions of pure rotational lines can now be produced up to the THz region. On the basis of these spectroscopic predictions, we report the interstellar detection of aminoacetonitrile in its v_11_=1 and v_18_=1 vibrational states toward Sgr B2(N1) in addition to emission in its vibrational ground state. The intensities of the identified v_11_=1 and v_18_=1 lines are consistent with the detected v=0 lines under LTE at a temperature of 200K for an aminoacetonitrile column density of 1.1x10^17^/cm^2^. This work shows the strong interplay between laboratory spectroscopy exploiting (sub)millimeter and synchrotron far-infrared techniques, and observational spectral surveys to detect complex organic molecules in space and quantify their abundances.
- ID:
- ivo://CDS.VizieR/J/ApJ/757/46
- Title:
- Hot methane (CH4) line list
- Short Name:
- J/ApJ/757/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present comprehensive experimental line lists of methane (CH_4_) at high temperatures obtained by recording Fourier transform infrared emission spectra. Calibrated line lists are presented for the temperatures 300-1400{deg}C at twelve 100{deg}C intervals spanning the 960-5000/cm (2.0-10.4{mu}m) region of the infrared. This range encompasses the dyad, pentad, and octad regions, i.e., all fundamental vibrational modes along with a number of combination, overtone and hot bands. Using our CH_4_ spectra, we have estimated empirical lower state energies (E_low_ in cm^-1^) and our values have been incorporated into the line lists along with line positions ({nu} in cm^-1^) and calibrated line intensities (S' in cm/molecule). We expect our hot CH_4_ line lists to find direct application in the modeling of planetary atmospheres and brown dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A184
- Title:
- HSCO^+^ and DSCO^+^ lines
- Short Name:
- J/A+A/620/A184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Protonated molecular species have been proven to be abundant in the interstellar gas. This class of molecules is also pivotal for the determination of important physical parameters for the ISM evolution (e.g. gas ionisation fraction) or as tracers of non-polar, hence not directly observable, species. The identification of these molecular species through radioastronomical observations is directly linked to a precise laboratory spectral characterisation. The goal of the present work is to extend the laboratory measurements of the pure rotational spectrum of the ground electronic state of protonated carbonyl sulfide (HSCO^+^) and its deuterium substituted isotopomer (DSCO^+^). At the same time, we show how implementing different laboratory techniques allows the determination of different spectroscopical properties of asymmetric-top protonated species. Three different high-resolution experiments were involved to detected for the first time the b-type rotational spectrum of HSCO^+^, and to extend, well into the sub-millimeter region, the a-type spectrum of the same molecular species and DSCO^+^. The electronic ground-state of both ions have been investigated in the 273-405GHz frequency range, allowing the detection of 60 and 50 new rotational transitions for HSCO^+^ and DSCO^+^, respectively. The combination of our new measurements with the three rotational transitions previously observed in the microwave region permits the rest frequencies of the astronomically most relevant transitions to be predicted to better than 100kHz for both HSCO^+^ and DSCO^+^ up to 500GHz, equivalent to better than 60m/s in terms of equivalent radial velocity. The present work illustrates the importance of using different laboratory techniques to spectroscopically characterise a protonated species at high frequency. Each instruments addressed complementary part of the same spectroscopic challenge, showing that a similar approach can be adopted in the future when dealing with similar reactive species.
327. HSO line list
- ID:
- ivo://CDS.VizieR/J/A+A/591/A126
- Title:
- HSO line list
- Short Name:
- J/A+A/591/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Despite the fact that many sulfur-bearing molecules, ranging from simple diatomic species up to astronomical complex molecules, have been detected in the interstellar medium, the sulfur chemistry in space is largely unknown and a depletion in the abundance of S-containing species has been observed in the cold, dense interstellar medium. The chemical form of the missing sulfur has yet to be identified. For these reasons, in view of the fact that there is a large abundance of triatomic species harbouring sulfur, oxygen, and hydrogen, we decided to investigate the HSO radical in the laboratory to try its astronomical detection. High-resolution measurements of the rotational spectrum of the HSO radical were carried out within a frequency range well up into the THz region. Subsequently, a rigorous search for HSO in the two most studied high-mass star-forming regions, Orion KL and Sagittarius (Sgr) B2, and in the cold dark cloud Barnard 1 (B1-b) was performed.
- ID:
- ivo://CDS.VizieR/J/A+AS/141/297
- Title:
- H_2_ total transition probability
- Short Name:
- J/A+AS/141/297
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The tables display the total emission probabilities, the total dissociation probabilities and the mean kinetic energies released in the dissociation for the rovibronic levels of B, C, B' and D states. As these states are mixed together, we have labeled and ordered them according to the Born Oppenheimer state of greatest weight. For each rovibrational state they display also the term value and the weight of Born Oppenheimer states B, C, B', D defined in eq (6) of the paper.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/2332
- Title:
- Hydrogen Lyman and Balmer line profiles
- Short Name:
- J/MNRAS/448/2332
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new calculations of unified line profiles for hydrogen perturbed by collisions with protons. We report on new calculations of the potential energies and dipole moments which allow the evaluation of profiles for the lines of the Lyman series up to Lyman {delta} and the Balmer series up to Balmer 10. Unified calculations only existed for the lines Lyman {alpha} to Lyman {gamma} and Balmer {alpha} including the H_2_^+^ quasi-molecule. These data are available as online material accompanying this paper and should be included in atmosphere models, in place of the Stark effect of protons, since the quasi-molecular contributions cause not only satellites, but large asymmetries that are unaccounted for in models that assume that Stark broadening of electrons and that of protons are equal.
- ID:
- ivo://CDS.VizieR/J/ApJ/716/1315
- Title:
- Hyperfine levels of N_2_H^+^
- Short Name:
- J/ApJ/716/1315
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we discuss two approximate methods previously suggested for modeling hyperfine spectral line emission for molecules whose collisional transition rates between hyperfine levels are unknown. Hyperfine structure is seen in the rotational spectra of many commonly observed molecules such as HCN, HNC, NH_3_, N_2_H^+^, and C^17^O. The intensities of these spectral lines can be modeled by numerical techniques such as {Lambda}-iteration that alternately solve the equations of statistical equilibrium and the equation of radiative transfer. However, these calculations require knowledge of both the radiative and collisional rates for all transitions. For most commonly observed radio frequency spectral lines, only the net collisional rates between rotational levels are known. For such cases, two approximate methods have been suggested. The first method, hyperfine statistical equilibrium, distributes the hyperfine level populations according to their statistical weight, but allows the population of the rotational states to depart from local thermal equilibrium (LTE). The second method, the proportional method, approximates the collision rates between the hyperfine levels as fractions of the net rotational rates apportioned according to the statistical degeneracy of the final hyperfine levels. The second method is able to model non-LTE hyperfine emission. We compare simulations of N_2_H^+^ hyperfine lines made with approximate and more exact rates and find that satisfactory results are obtained.
