- ID:
- ivo://CDS.VizieR/J/ApJS/167/334
- Title:
- Radiative recombination data for plasmas
- Short Name:
- J/ApJS/167/334
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have calculated partial final-state resolved radiative recombination (RR) rate coefficients from the initial ground and metastable levels of all elements up to and including Zn, plus Kr, Mo, and Xe, for all isoelectronic sequences up to Na-like forming Mg-like. The data are archived according to the Atomic Data and Analysis Structure (ADAS) data class adf48, which spans a temperature range of z^2^(10^1^-10^7^)K, where z is the initial ion charge. Fits to total rate coefficients have been determined, for both the ground and metastable levels, and those for the ground are presented here. Comparison is made both with previous RR rate coefficients and with (background) R-matrix photoionization cross sections. This RR database complements a dielectronic recombination (DR) database already produced, and both are being used to produce updated ionization balances for both (electron) collisionally ionized and photoionized plasmas.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/599/A10
- Title:
- Radiative recombination electron energy loss data
- Short Name:
- J/A+A/599/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For photoionized plasmas, electron energy loss rates due to radiative recombination (RR) are required for thermal equilibrium calculations, which assume a local balance between the energy gain and loss. While many calculations of total and/or partial RR rates are available from the literature, specific calculations of associated RR electron energy loss rates are lacking. Here we focus on electron energy loss rates due to radiative recombination of H-like to Ne-like ions for all the elements up to and including zinc (Z=30), over a wide temperature range. We used the AUTOSTRUCTURE code to calculate the level-resolved photoionization cross section and modify the ADASRR code so that we can simultaneously obtain level-resolved RR rate coefficients and associated RR electron energy loss rate coefficients. We compared the total RR rates and electron energy loss rates of HI and HeI with those found in the literature. Furthermore, we utilized and parameterized the weighted electron energy loss factors (dimensionless) to characterize total electron energy loss rates due to RR. The RR electron energy loss data are archived according to the Atomic Data and Analysis Structure (ADAS) data class adf48. The RR electron energy loss data are also incorporated into the SPEX code for detailed modeling of photoionized plamsas.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/30
- Title:
- Raman scattering cross sections for H_2_
- Short Name:
- J/ApJ/832/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An important source of opacity in exoplanet atmospheres at short visible and near-UV wavelengths is Rayleigh scattering of light on molecules. It is accompanied by a related, albeit weaker process-Raman scattering. We analyze the signatures of Raman scattering imprinted in the reflected light and the geometric albedo of exoplanets, which could provide information about atmospheric properties. Raman scattering affects the geometric albedo spectra of planets in the following ways. First, it causes filling-in of strong absorption lines in the incident radiation, thus producing sharp peaks in the albedo. Second, it shifts the wavelengths of spectral features in the reflected light causing the so-called Raman ghost lines. Raman scattering can also cause a broadband reduction of the albedo due to wavelength shifting of a stellar spectrum with red spectral index. Observing the Raman peaks in the albedo could be used to measure the column density of gas, thus providing constraints on the presence of clouds in the atmosphere. Observing the Raman ghost lines could be used to spectroscopically identify the main scatterer in the atmosphere, even molecules like H_2_ or N_2_, which do not have prominent spectral signatures in the optical wavelength range. If detected, ghost lines could also provide information about the temperature of the atmosphere. In this paper, we investigate the effects of Raman scattering in hydrogen- and nitrogen-dominated atmospheres. We analyze the feasibility of detecting the signatures of Raman scattering with the existing and future observational facilities, and of using these signatures as probes of exoplanetary atmospheres.
- ID:
- ivo://CDS.VizieR/J/ApJS/182/80
- Title:
- Rare earth abundances
- Short Name:
- J/ApJS/182/80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived new abundances of the rare earth elements Pr, Dy, Tm, Yb, and Lu for the solar photosphere and for five very metal-poor, neutron-capture r-process-rich giant stars. The photospheric values for all five elements are in good agreement with meteoritic abundances. For the low-metallicity sample, these abundances have been combined with new Ce abundances from a companion paper, and reconsideration of a few other elements in individual stars, to produce internally consistent Ba, rare earth, and Hf(56<=Z<=72) element distributions. These have been used in a critical comparison between stellar and solar r-process abundance mixes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/503/1976
- Title:
- Rate coefficients and ion populations
- Short Name:
- J/MNRAS/503/1976
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To predict line emission in the solar atmosphere requires models which are fundamentally different depending on whether the emission is from the chromosphere or the corona. At some point between the two regions, there must be a change between the two modelling regimes. Recent extensions to the coronal modelling for carbon and oxygen lines in the solar transition region have shown improvements in the emission of singly- and doubly-charged ions, along with Li-like ions. However, discrepancies still remain, particularly for singly-charged ions and intercombination lines. The aim of this work is to explore additional atomic processes that could further alter the charge state distribution and the level populations within ions, in order to resolve some of the discrepancies. To this end, excitation and ionisation caused by both the radiation field and by atom-ion collisions have been included, along with recombination through charge transfer. The modelling is carried out using conditions which would be present in the quiet Sun, which allows an assessment of the part atomic processes play in changing coronal modelling, separately from dynamic and transient events taking place in the plasma. The effect the processes have on the fractional ion populations are presented, as well as the change in level populations brought about by the new excitation mechanisms. Contribution functions of selected lines from low charge states are also shown, to demonstrate the extent to which line emission in the lower atmosphere could be affected by the new modelling.
- ID:
- ivo://CDS.VizieR/J/ApJ/827/62
- Title:
- Rate coefficients for H_2_(v,j)+H_2_(v',j')
- Short Name:
- J/ApJ/827/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- State-specific rate coefficients for the dissociation of H_2_ as the result of collisions with H_2_ were calculated for all combinations of (v,j) with an internal energy below 1eV. Full-dimensional quasiclassical trajectories were calculated using the BMKP2 interaction potential with a minimum of 80000 trajectories at each translational energy. Additional large batches of trajectories were carried out to calculate the cross sections near the threshold to dissociation to attain the desired precision of the rate coefficients. A piecewise linear excitation function was used to calculate the rate coefficient between 100 and 100000K. The resulting state-specific rate coefficients, {gamma}, were parametrized as a function of temperature over the range 600-10000K using: log_10_{gamma}(t)=a+bz+cz^2^-d(1/t-1) where t=T/4500K and z=log_10_t. The values of the resulting rate coefficients were sensitive to the internal energy of both molecules, with initial vibrational energy having a slightly greater effect than rotational energy. This effect diminished as temperature increased.
- ID:
- ivo://CDS.VizieR/J/A+A/466/641
- Title:
- Reaction rates of NeNa-MgAl chains in AGB stage
- Short Name:
- J/A+A/466/641
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We test the effect of proton-capture reaction rate uncertainties on the abundances of the Ne, Na, Mg and Al isotopes processed by the NeNa and MgAl chains during hot bottom burning (HBB) in asymptotic giant branch (AGB) stars of intermediate mass between 4 and 6M_{sun}_ and metallicities between Z=0.0001 and 0.02. We provide uncertainty ranges for the AGB stellar yields, for inclusion in galactic chemical evolution models, and indicate which reaction rates are most important and should be better determined.
- ID:
- ivo://CDS.VizieR/J/ApJ/748/99
- Title:
- Reactions of acetic acid with hydroxylamine
- Short Name:
- J/ApJ/748/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A computational study of the reactions of hydroxylamine and its ionized and protonated derivatives with acetic acid is provided. The reaction of neutral hydroxylamine with acetic acid, despite being clearly exothermic, involves a very large energy barrier. The reaction of ionized hydroxylamine with acetic acid is also clearly exothermic, but again a significant energy barrier is found (around 24 kcal/mol at the CCSD(T) level). The reaction of the most stable protonated isomer of hydroxylamine, NH_3_OH^+^, with acetic acid also involves a high barrier (more than 27 kcal/mol at the CCSD(T) level). Only the higher energy isomer, NH_2_OH^+^_2_, leads to a sensibly lower energy barrier (about 2.3 kcal/mol at the CCSD(T) level). Nevertheless, an estimate of the reaction coefficient at low temperatures such as those reigning in the interstellar medium gives very low values. Therefore, it seems that precursors of interstellar glycine could not be efficiently produced from the reactions of hydroxylamine-derived ions with acetic acid.
- ID:
- ivo://CDS.VizieR/J/A+AS/142/85
- Title:
- Recombination coefficients for C II lines
- Short Name:
- J/A+AS/142/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Effective recombination coefficients are given for C II transitions between doublet states. The calculations are carried out in the temperature range 500-20000K and for an electron density of 10^4^cm^-3^. The effects of electron collisions on the excited states are included. The necessary bound-bound and bound-free radiative data are obtained from a new R-matrix calculation in which photoionization resonances are fully delineated, thereby accurately incorporating the effects of both radiative and dielectronic recombination. The R-matrix calculation includes all bound states with principal quantum number n<=15 and total orbital angular momentum L<=4. The effect of moving the resonance features to their experimentally determined positions is also investigated and found to be important at low temperatures.
- ID:
- ivo://CDS.VizieR/J/A+AS/133/257
- Title:
- Recombination coefficients for NeII lines
- Short Name:
- J/A+AS/133/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We calculate total recombination coefficients for Ne^2+^ + e^-^ and effective recombination coefficients for the formation of selected lines of Ne II. New photoionization data are calculated which accurately map the near threshold resonances and are used to derive recombination coefficients for principal quantum numbers, n<=15, including radiative and dielectronic recombination. Cascading from higher states is included, allowing for the effects of finite electron density in a hydrogenic approximation. The effects of population in the excited states of the recombining ion are investigated.
