- ID:
- ivo://CDS.VizieR/VI/150
- Title:
- Recombination coefficients for O II lines - SSB2
- Short Name:
- VI/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a calculation of recombination coefficientscients for O^2 + ^+e^-^ using an intermediate coupling treatment that fully accounts for the dependence of the distribution of population among the ground levels of O^2+^ on electron density and temperature. The calculation is extended down to low electron temperatures where dielectronic recombination arising from Rydberg states converging on the O^2+^ ground levels is an important process. The data, which consist of emission coefficientscients for 8889 recombination lines and recombination coefficientscients for the ground and metastable states of O^+^ are in Cases A, B and C, and are organised as a function of the electron temperature and number density, as well as wavelength. An interactive fortran 77 data server is also provided as an accessory for mining the line emission coefficients and obtaining Lagrange interpolated values for any choice of the two variables between the explicitly provided values for any set of wavelengths. Some illustrations of the application of the new data to nebular observations are also provided.
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Search Results
- ID:
- ivo://CDS.VizieR/VI/64
- Title:
- Recombination line intensities for hydrogenic ions
- Short Name:
- VI/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Line emissivities, effective recombination coefficients, opacity factors, departure coefficients and total recombination coefficients are calculated for hydrogenic ions with Z<=8. There are 162 primary files labelled rZCTTTT.d, where Z=1,2,..,8 is the ionic charge C=a or b is the Case in the sense of Baker and Menzel (1938ApJ....88...52B), i.e. -- A for a nebula transparent to Lyman line radiation, -- B for an opaque nebula TTTT=0.01Te is a reduced temperature variable. There are 9 values of electron densities (log(Ne)=2(1)10) for case A, and 13 (log(Ne)=2(1)14) for case B. The structure of these files is detailed in section 4 of the MNRAS paper. There are 16 secondary files labelled eZC.d, where Z=1,2,..,8 is the ionic charge C=a or b is the Case in the sense of Baker and Menzel (1938ApJ....88...52B) which contain emissivities and total recombination coefficients. These files are accompanied by an interactive data server intrat.f. Please refer to section 5 of the MNRAS paper which details the usage of the program. CGS units are used, meaning that => densities are expressed in cm^-3^ => emissivities are expressed in erg.s^-1^.cm^-3^ (10^-7^W.cm^-3^) => effective recombination coefficients are expressed in cm^3^.s^-1^
- ID:
- ivo://CDS.VizieR/J/ApJS/63/661
- Title:
- Relativistic Free-Free Gaunt Factor
- Short Name:
- J/ApJS/63/661
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The free-free Gaunt factor of the dense high-temperature stellar plasma is calculated by using the accurate relativistic cross section and is compared with the Gaunt factor derived by using Sommerfeld's exact nonrelativistic cross section. A wide range of electron degeneracy is accurately taken into account. Significant deviations from the nonrelativistic results are found for high-temperature cases. Results are presented in the form of extensive tables to facilitate applications.
- ID:
- ivo://CDS.VizieR/J/ApJS/74/291
- Title:
- Relativistic Free-Free Gaunt Factor. II.
- Short Name:
- J/ApJS/74/291
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The pure Coulomb free-free Gaunt factors of the dense high-temperature carbon and oxygen plasmas are calculated by using the accurate relativistic cross section and are compared with the Gaunt factors derived by using Sommerfeld's exact nonrelativistic cross section. A wide range of electron degeneracy is accurately taken into account. Effects from resonances in the free electron density of states are not included. Dramatic deviations from the nonrelativistic results are found for high-temperature cases. Results are presented in the form of extensive tables to facilitate applications.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/13
- Title:
- Relativistic MR-MP energy levels for Si
- Short Name:
- J/ApJS/234/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Level energies are reported for Si V, Si VI, Si VII, Si VIII, Si IX, Si X, Si XI, and Si XII. The energies have been calculated with the relativistic Multi- Reference Moller-Plesset Perturbation Theory method and include valence and K-vacancy states with nl up to 5f. The accuracy of the calculated level energies is established by comparison with the recommended data listed in the National Institute of Standards and Technology (NIST) online database. The average deviation of valence level energies ranges from 0.20eV in SiV to 0.04eV in SiXII. For K-vacancy states, the available values recommended in the NIST database are limited to Si XII and Si XIII. The average energy deviation is below 0.3eV for K-vacancy states. The extensive and accurate data set presented here greatly augments the amount of available reference level energies. We expect our data to ease the line identification of L-shell ions of Si in celestial sources and laboratory-generated plasmas, and to serve as energy references in the absence of more accurate laboratory measurements.
- ID:
- ivo://CDS.VizieR/J/A+A/492/875
- Title:
- Rest frequencies for C3O
- Short Name:
- J/A+A/492/875
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The submillimetre-wave spectrum of C3O (X^1^{Sigma}^+^) has been investigated in the laboratory using a source-modulation microwave spectrometer equipped with a gas-phase flow pyrolysis system for the production of unstable chemical species. C3O was produced by thermal decomposition of fumaryl chloride at 900{deg}C. Thirty-seven new rotational transitions were observed in the frequency range 307-740GHz for the ground vibrational state, reaching a J quantum number as high as 76. Additionally, new millimetre-wave and submillimetre-wave lines were recorded for the bending fundamental v5=1, and for its overtone v5=2 and v5=3 whose rotational spectra have been identified for the first time. The new laboratory measurements provide much improved rest frequencies in the submillimetre spectral region for the ground state spectra of C3O, and for the first levels of its low-energy v5 vibrational ladder, useful for the radioastronomical identification of the irrotational lines in the ISM.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A56
- Title:
- Rest frequencies of dithioformic acid
- Short Name:
- J/A+A/612/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A better understanding of sulphur chemistry is needed to solve the interstellar sulphur depletion problem. A way to achieve this goal is to study new S-bearing molecules in the laboratory, obtaining accurate rest frequencies for an astronomical search. We focus on dithioformic acid, HCSSH, which is the sulphur analogue of formic acid. The aim of this study is to provide an accurate line list of the two HCSSH trans and cis isomers in their electronic ground state and a comprehensive centrifugal distortion analysis with an extension of measurements in the millimetre and submillimetre range. We studied the two isomers in the laboratory using an absorption spectrometer employing the frequency-modulation technique. The molecules were produced directly within a free-space cell by glow discharge of a gas mixture. We measured lines belonging to the electronic ground state up to 478GHz, with a total number of 204 and 139 new rotational transitions, respectively, for trans and cis isomers. The final dataset also includes lines in the centimetre range available from literature. The extension of the measurements in the mm and submm range lead to an accurate set of rotational and centrifugal distortion parameters. This allows us to predict frequencies with estimated uncertainties as low as 5kHz at 1mm wavelength. Hence, the new dataset provided by this study can be used for astronomical search.
- ID:
- ivo://CDS.VizieR/J/A+A/621/A111
- Title:
- Rest frequencies of ketenyl (HCCO and DCCO)
- Short Name:
- J/A+A/621/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ketenyl radical, HCCO, has recently been detected in the ISM for the first time. Further astronomical detections of HCCO will help us understand its gas-grain chemistry, and subsequently revise the oxygen-bearing chemistry towards dark clouds. Moreover, its deuterated counterpart, DCCO, has never been observed in the ISM. HCCO and DCCO still lack of a broad spectroscopic investigation although they exhibit a significant astrophysical relevance. In this work we aim to measure the pure rotational spectra of the ground state of HCCO and DCCO in the millimeter and submillimeter region, considerably extending the frequency range covered by previous studies. The spectral acquisition was performed using a frequency-modulation absorption spectrometer between 170 and 650GHz. The radicals were produced in a low-density plasma generated from a select mixture of gaseous precursors. For each isotopologue we were able to detect and assign more than 100 rotational lines. The new lines have significantly enhanced the previous data set allowing the determination of highly precise rotational and centrifugal distortion parameters. In our analysis we have taken into account the interaction between the ground electronic state and a low-lying excited state (Renner-Teller pair) which enables the prediction and assignment of rotational transitions with Ka up to 4. The present set of spectroscopic parameters provides highly accurate, millimeter and submillimeter rest-frequencies of HCCO and DCCO for future astronomical observations. We also show that towards the pre-stellar core L1544, ketenyl peaks in the region where c-C_3_H_2_ peaks, suggesting that HCCO follows a predominant hydrocarbon chemistry, as already proposed by recent gas-grain chemical models.
- ID:
- ivo://CDS.VizieR/J/A+A/428/1019
- Title:
- Rest frequencies of methanol maser lines
- Short Name:
- J/A+A/428/1019
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report accurate laboratory measurements of selected methanol transition frequencies between 0.834 and 230GHz in order to facilitate astronomical velocity analyses. New data have been obtained between 10 and 27GHz and between 60 and 119GHz. Emphasis has been put on known or potential interstellar maser lines as well as on transitions suitable for the investigation of cold dark clouds. Because of the narrow line widths (<0.5km/s) of maser lines and lines detected in dark molecular clouds, accurate frequencies are needed for comparison of the velocities of different methanol lines with each other as well as with lines from other species. In particular, frequencies for a comprehensive set of transitions are given which, because of their low energy levels (<20cm^-1^ or 30K), are potentially detectable in cold clouds. Global Hamiltonian fits generally do not yet yield the required accuracy. Additionally, we report transition frequencies for other lines that may be used to test and to improve existing Hamiltonian models.
- ID:
- ivo://CDS.VizieR/J/A+A/455/1161
- Title:
- Rest frequencies of sub-mm spectrum of SiN
- Short Name:
- J/A+A/455/1161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The submillimetre-wave spectrum of the SiN radical has been investigated in the laboratory using a source-modulation microwave spectrometer equipped with a negative glow discharge cell. SiN was produced in a SiCl_4_/N_2_ discharge plasma. Twenty-one new fine and hyperfine components up to N=17-16 were observed reaching a frequency as high as 740GHz. The new laboratory measurements provide much improved rest frequencies in the submillimetre spectral region useful for the identification of SiN lines in hot core sources and circumstellar shells.
