- ID:
- ivo://CDS.VizieR/J/ApJ/738/5
- Title:
- Effective collision strengths in NiII
- Short Name:
- J/ApJ/738/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present collision strengths and Maxwellian averaged effective collision strengths for the electron-impact excitation of NiII. Attention is expressly concentrated on the optically allowed fine-structure transitions between the 3d^9^, 3d^8^4s, and 3d^7^4s^2^ even parity levels and the 3d^8^4p and 3d^7^4s 4p odd parity levels. The parallel RMATRXII R-matrix package has been recently extended to allow for the inclusion of relativistic fine-structure effects. This suite of codes has been utilized in conjunction with the parallel PSTGF and PSTGICF programs in order to compute converged total collision strengths for the allowed transitions with which this study is concerned. All 113 LS terms identified with the 3d^9^, 3d^8^4s, 3d^7^4s^2^, 3d^8^4p, and 3d^7^4s 4p basis configurations were included in the target wavefunction representation, giving rise to a sophisticated 295 jj-level, 1930 coupled channel scattering complex. Maxwellian averaged effective collision strengths have been computed at 30 individual electron temperatures ranging from 30 to 1000000K. This range comfortably encompasses all temperatures significant to astrophysical and plasma applications.
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- ID:
- ivo://CDS.VizieR/J/A+A/524/A35
- Title:
- Effective collision strengths of CrII
- Short Name:
- J/A+A/524/A35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Absorption or emission lines of Cr II are observed in a wide variety of astrophysical spectra and accurate atomic data are urgently needed to interpret these lines. Many of these data are impossible to measure experimentally and a full theoretical treatment is the only means by which these data can be obtained.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/206
- Title:
- Effective collision strengths of FeVIII
- Short Name:
- J/ApJ/743/206
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New extensive calculations are reported for electron collision strengths, rate coefficients, and transition probabilities for the astrophysically important lines of FeVIII. The collision strengths have been calculated in the close-coupling approximation using the B-spline Breit-Pauli R-matrix method (BSR) code (Zatsarinny 2006CoPhC.174..273Z). The multiconfiguration Hartree-Fock method with term-dependent non-orthogonal orbitals is employed for an accurate representation of the target wave functions. The close-coupling expansion includes 102 fine-structure levels of FeVIII covering all possible terms of the ground 3p^6^3d and singly excited 3p^5^3d^2^, 3p^6^4l, 3p^5^3d4s, 3s3p^6^3d^2^, and 3p^6^5l configurations. The present calculations are more extensive than the previous ones, leading to a total 5151 transitions between fine-structure levels. The effective collision strengths are obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities and these are tabulated for all fine-structure transitions at electron temperatures in the range from 5x10^3^ to 5x10^6^K. There is an overall good agreement with the previous 77-state calculations by Griffin, Pindzola, & Badnell (2000A&AS..142..317G), but significant differences are also noted for some transitions.
- ID:
- ivo://CDS.VizieR/J/A+A/513/A55
- Title:
- Effective collision strengths of Ni II
- Short Name:
- J/A+A/513/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Considerable demand exists for electron excitation data for Ni II, since lines from this abundant ion are observed in a wide variety of laboratory and astrophysical spectra. The accurate theoretical determination of these data can present a significant challenge however, due to complications arising from the presence of an open 3d-shell in the description of the target ion.
- ID:
- ivo://CDS.VizieR/J/ApJ/787/2
- Title:
- Effective collision strengths of Si VII
- Short Name:
- J/ApJ/787/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The effective collision strengths for electron-impact excitation of fine-structure transitions in Si VII are calculated as a function of electron temperature in the range 5000-2000000 K. The B-spline Breit-Pauli R-matrix method has been used to calculate collision strengths by electron impact. The target wave functions have been obtained using the multi-configuration Hartree-Fock method with term-dependent non-orthogonal orbitals. The 92 fine-structure levels belonging to the 46 LS states of 2s^2^2p^4^, 2s2p^5^, 2p^6^, 2s^2^2p^3^3s, 2s^2^2p^3^3p, 2s^2^2p^3^3d, and 2s2p^4^3s configurations are included in our calculations of oscillator strengths and collision strengths. There are 4186 possible fine-structure allowed and forbidden transitions among the 92 levels. The present excitation energies, oscillator strengths, and collision strengths have been compared with previous theoretical results and available experimental data. Generally, a good agreement is found with the 6 LS-state close-coupling approximation results of Butler & Zeippen (1994, J/A+AS/108/1) and the 44 LS-state distorted wave calculation of Bhatia & Landi (2003ApJ...585..587B).
- ID:
- ivo://CDS.VizieR/J/ApJS/208/10
- Title:
- Effects of a {kappa}-distribution in HII regions
- Short Name:
- J/ApJS/208/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recently, Nicholls et al. (2012ApJ...752..148N), inspired by in situ observations of solar system astrophysical plasmas, suggested that the electrons in H II regions are characterized by a {kappa}-distribution of energies rather than a simple Maxwell-Boltzmann distribution. Here, we have collected together new atomic data within a modified photoionization code to explore the effects of both the new atomic data and the {kappa}-distribution on the strong-line techniques used to determine chemical abundances in H II regions. By comparing the recombination temperatures (T_rec_) with the forbidden line temperatures (T_FL_), we conclude that {kappa}~20. While representing only a mild deviation from equilibrium, this result is sufficient to strongly influence abundances determined using methods that depend on measurements of the electron temperature from forbidden lines. We present a number of new emission line ratio diagnostics that cleanly separate the two parameters determining the optical spectrum of H II regions--the ionization parameter q or {} and the chemical abundance, 12+log(O/H). An automated code to extract these parameters is presented. Using the homogeneous data set from van Zee et al. 1998, Cat. J/AJ/116/2805, we find self-consistent results between all of these different diagnostics. The systematic errors between different line ratio diagnostics are much smaller than those found in the earlier strong-line work. Overall, the effect of the {kappa}-distribution on the strong-line abundances derived solely on the basis of theoretical models is rather small.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A126
- Title:
- Effects of a revised ^7^Be e^-^-capture rate
- Short Name:
- J/A+A/623/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The electron-capture rate on ^7^Be is the main production channel for ^7^Li in several astrophysical environments. Theoretical evaluations have to account for not only the nuclear interaction, but also the processes in the plasma where ^7^Be ions and electrons interact. In the past decades several estimates were presented, pointing out that the theoretical uncertainty in the rate is in general of few percents. In the framework of fundamental solar physics, we consider here a recent evaluation for the ^7^Be+e^-^ rate, not used up to now in the estimate of neutrino fluxes. We analysed the effects of the new assumptions on Standard Solar Models (SSMs) and compared the results obtained by adopting the revised ^7^Be+e^-^ rate to those obtained by the one reported in a widely used compilation of reaction rates (ADE11). We found that new SSMs yield a maximum difference in the efficiency of the ^7^Be channel of about -4% with respect to what is obtained with the previously adopted rate. This fact affects the production of neutrinos from ^8^B, increasing the relative flux up to a maximum of 2.7%. Negligible variations are found for the physical and chemical properties of the computed solar models. The agreement with the SNO measurements of the neutral current component of the ^8^B neutrino flux is improved
- ID:
- ivo://CDS.VizieR/J/ApJS/229/34
- Title:
- Effects of preionization in radiative shocks
- Short Name:
- J/ApJS/229/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we treat the preionization problem in shocks over the velocity range 10<v_s_<1500km/s in a self-consistent manner. We identify four distinct classes of solutions controlled by the value of the shock-precursor parameter, {Psi}=Q/v_s_, where Q is the ionization parameter of the UV photons escaping upstream. This parameter determines both the temperature and the degree of ionization of the gas entering the shock. In increasing velocity, the shock solution regimes are cold neutral precursors (v_s_<~40km/s), warm neutral precursors (40<~v_s_<~75km/s), warm partly ionized precursors (75<~v_s_<~120km/s), and fast shocks in which the preshock gas is in photoionization equilibrium and is fully ionized. The main effect of a magnetic field is to push these velocity ranges to higher values and to limit the postshock compression. In order to facilitate comparison with observations of shocks, we provide a number of convenient scaling relationships for parameters, such as postshock temperature, compression factors, cooling lengths, and H{beta} and X-ray luminosity.
- ID:
- ivo://CDS.VizieR/J/ApJ/698/2114
- Title:
- Einstein A coeff. for ^12^C_2_D_2_ transitions
- Short Name:
- J/ApJ/698/2114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two hundred and fifty-one ^12^C_2_D_2_ transitions have been measured in the 0.2-1.6THz region of its nu_5_-nu_4_ difference band and 202 of them were observed for the first time. The accuracy of these measurements is estimated to be ranging from 50kHz to 100kHz. The ^12^C_2_D_2_ molecules were generated under room temperature by passing 120-150mTorr D_2_O vapor through calcium carbide (CaC_2_) powder. A multistate analysis was carried out for the bending vibrational modes nu_4_ and nu_5_ of ^12^C_2_D_2_, which includes the lines observed in this work and prior microwave, far-infrared and infrared data on the pure bending levels. Significantly improved molecular parameters were obtained for ^12^C_2_D_2_ by adding the new measurements to the old data set, which had only 10 lines with microwave measurement precision. New frequency and intensity predictions have been made based on the obtained molecular parameters. The more precise measurements and new predictions reported here will support the analyses of astronomical observations by the future high-resolution spectroscopy telescopes such as Herschel, SOFIA, and ALMA, which will work in the terahertz spectral region.
- ID:
- ivo://CDS.VizieR/J/A+A/376/333
- Title:
- Einstein A-coefficients for C_3_H_4_
- Short Name:
- J/A+A/376/333
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Following tentative detection of cyclopropene (C_3_H_4_) in Sgr B2 through its transition 3_22_-2_21_, several attempts to confirm the presence of cyclopropene in astronomical objects (including Sgr B2 itself) have been made. We suggest that cyclopropene may be observed in astronomical objects through its transition 2_20_-2_21_ at 3.67218GHz, in absorption, even against the cosmic 2.7K background, in a region having low density and low kinetic temperature.
