Quantum study of inelastic processes in low-energy calcium–hydrogen collisions

2019 ◽  
Vol 490 (3) ◽  
pp. 3384-3391 ◽  
Author(s):  
A K Belyaev ◽  
D V Vlasov ◽  
A Mitrushchenkov ◽  
N Feautrier
Keyword(s):  
Cross Sections ◽  
Binding Energies ◽  
Rate Coefficients ◽  
Atomic Data ◽  
Nuclear Dynamics ◽  
Covalent Interactions ◽  
Diabatic Representation ◽  
Optimal Window ◽  
Quantum Chemical Data ◽  
Inelastic Processes

ABSTRACT Cross-sections and rate coefficients for the partial inelastic processes in calcium–hydrogen collisions are calculated by means of the quantum reprojection method for nuclear dynamics based on the accurate ab initio electronic structure data. That is, the atomic data for the 110 inelastic processes of excitation, de-excitation, ion-pair formation, and mutual neutralization in Ca  + H and Ca+  + H− collisions are computed for all transitions between the 11 low-lying CaH(2Σ+) molecular states including ionic one. The quantum chemical data are used in a hybrid diabatic representation, which is derived from the adiabatic representation. It is found that the largest rate coefficients correspond to the mutual neutralization processes. At the temperature 6000 K, the maximal rate is equal to $4.37 \times 10^{-8}\, \mathrm{cm}^{3}\,\mathrm{s}^{-1}$. It is shown that the large-valued rates are determined by long-range ionic–covalent interactions with final binding energies from the optimal window, while moderate- and low-valued rates by both long- and short-range non-adiabatic regions with final energies outside of the optimal window.

scholarly journals Improved Neutron-Capture Element Abundances in Planetary Nebulae

2009 ◽  
Vol 26 (3) ◽  
pp. 339-344 ◽  
Author(s):  
N. C. Sterling ◽  
H. L. Dinerstein ◽  
S. Hwang ◽  
S. Redfield ◽  
A. Aguilar ◽  
...  
Keyword(s):  
Cross Sections ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Rate Coefficients ◽  
Atomic Data ◽  
Agb Stars ◽  
Iron Species ◽  
Element Abundances ◽  
Ionization Balance ◽  
Initial Results

AbstractSpectroscopy of planetary nebulae (PNe) provides the means to investigate s-process enrichments of neutron(n)-capture elements that cannot be detected in Asymptotic Giant Branch (AGB) stars. However, accurate abundance determinations of these elements present a challenge. Corrections for unobserved ions can be large and uncertain, since in many PNe only one ion of a given n-capture element has been detected. Furthermore, the atomic data governing the ionization balance of these species are not well-determined, inhibiting the derivation of accurate ionization corrections. We present initial results of a program that addresses these challenges. Deep high-resolution optical spectroscopy of ∼20 PNe has been performed to detect emission lines from trans-iron species including Se, Br, Kr, Rb and Xe. The optical spectral region provides access to multiple ions of these elements, which reduces the magnitude and importance of uncertainties in the ionization corrections. In addition, experimental and theoretical efforts are providing determinations of the photoionization cross sections and recombination rate coefficients of Se, Kr and Xe ions. These new atomic data will make it possible to derive robust ionization corrections for these elements. Together, our observational and atomic data results will enable n-capture element abundances to be determined with unprecedented accuracy in ionized nebulae.

Inelastic Processes in Copper-Hydrogen Collisions Including Fine Structure Effects

2020 ◽  
Author(s):  
Andrey K Belyaev ◽  
Svetlana A Yakovleva ◽  
Wolfgang P Kraemer
Keyword(s):  
Fine Structure ◽  
Rate Coefficient ◽  
Rate Coefficients ◽  
Coupling Scheme ◽  
Excitation Process ◽  
Nuclear Dynamics ◽  
Zener Model ◽  
A Value ◽  
Coupling Rate ◽  
Inelastic Processes

Abstract Inelastic processes in low-energy Cu + H and Cu+ + H− collisions, such as mutual neutralization, ion-pair formation, excitation, and de-excitation, 306 partial processes in total, are investigated taking fine structure effects into account. We use the asymptotic approach to model the adiabatic potentials and adapt a recently proposed method to include the copper fine structure. The nuclear dynamics is performed by making use of the multichannel analytical approach and the Landau-Zener model. The rate coefficients are calculated for the temperature range 1′000 − 10′000 K. The largest rate coefficient is obtained for the mutual neutralization process Cu+ + H− → Cu(3d105s 2S1/2) + H with a value of 3.81 × 10−8 cm3/s at a temperature of 6′000 K. The next lower rate coefficients with values below 10−8 cm3/s correspond to the partial processes of mutual neutralization ${\rm Cu}^{+} + {\rm H}^- \rightarrow {\rm Cu}(3d^{10}5p~^2P^{\circ }_{3/2, 1/2}) + {\rm H}$, Cu+ + H− → Cu(3d104d 2D3/2, 5/2) + H, and the de-excitation process ${\rm Cu}(3d^{10}4p~^2P^{\circ }_{1/2}) + {\rm H} \rightarrow {\rm Cu}(3d^{9}4s^2~^2D^{\circ }_{3/2, 5/2}) + {\rm H}$. It is shown that the practice to redistribute LS-coupling rate coefficients among fine structure sublevels can give rates which deviate significantly from those calculated in the JJ-coupling scheme, that is, with account for the fine structure effects.

scholarly journals Database NORAD-Atomic-Data for Atomic Processes in Plasma

Atoms ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 68
Author(s):  
Sultana Nahar
Keyword(s):  
Cross Sections ◽  
Ground State ◽  
Recombination Rate ◽  
Bound States ◽  
Transition Probabilities ◽  
Rate Coefficients ◽  
Atomic Data ◽  
Atomic Processes ◽  
Ion Recombination ◽  
Atomic Species

The online atomic database of NORAD-Atomic-Data, where NORAD stands for Nahar OSU Radiative, is part of the data sources of the two international collaborations of the Opacity Project (OP) and the Iron Project (IP). It contains large sets of parameters for the dominant atomic processes in astrophysical plasmas, such as, (i) photo-excitation, (ii) photoionization, (iii) electron–ion recombination, (iv) electron–impact excitations. The atomic parameters correspond to tables of energy levels, level-specific total photoionization cross-sections, partial photoionization cross-sections of all bound states for leaving the residual ion in the ground state, partial cross-sections of the ground state for leaving the ion in various excited states, total level-specific electron–ion recombination rate coefficients that include both the radiative and dielectronic recombination, total recombination rate coefficients summed from contributions of an infinite number of recombined states, total photo-recombination cross-sections and rates with respect to photoelectron energy, transition probabilities, lifetimes, collision strengths. The database was created after the first two atomic databases, TOPbase under the OP and TIPbase under the IP. Hence the contents of NORAD-Atomic-Data are either new or from repeated calculations using a much larger wave function expansion making the data more complete. The results have been obtained from the R-matrix method using the close-coupling approximation developed under the OP and IP, and from atomic structure calculations using the program SUPERSTRUCTURE. They have been compared with available published results which have been obtained theoretically and experimentally, and are expected to be of high accuracy in general. All computations were carried out using the computational facilities at the Ohio Supercomputer Center (OSC) starting in 1990. At present it contains atomic data for 154 atomic species, 98 of which are lighter atomic species with nuclear charge Z ≤ 28 and 56 are heavier ones with Z > 28. New data are added with publications.

scholarly journals Advances in atomic data for neutron-capture elements

2011 ◽  
Vol 7 (S283) ◽  
pp. 504-505
Author(s):  
Nicholas C. Sterling ◽  
Michael C. Witthoeft ◽  
David A. Esteves ◽  
Phillip C. Stancil ◽  
A. L. David Kilcoyne ◽  
...  
Keyword(s):  
Cross Sections ◽  
Accurate Determination ◽  
Photoionization Cross Section ◽  
Dielectronic Recombination ◽  
Rate Coefficients ◽  
Atomic Data ◽  
Ionization Equilibrium ◽  
Elemental Abundances ◽  
Progenitor Stars

AbstractNeutron(n)-capture elements (atomic number Z > 30), which can be produced in planetary nebula (PN) progenitor stars via s-process nucleosynthesis, have been detected in nearly 100 PNe. This demonstrates that nebular spectroscopy is a potentially powerful tool for studying the production and chemical evolution of trans-iron elements. However, significant challenges must be addressed before this goal can be achieved. One of the most substantial hurdles is the lack of atomic data for n-capture elements, particularly that needed to solve for their ionization equilibrium (and hence to convert ionic abundances to elemental abundances). To address this need, we have computed photoionization cross sections and radiative and dielectronic recombination rate coefficients for the first six ions of Se and Kr. The calculations were benchmarked against experimental photoionization cross section measurements. In addition, we computed charge transfer (CT) rate coefficients for ions of six n-capture elements. These efforts will enable the accurate determination of nebular Se and Kr abundances, allowing robust investigations of s-process enrichments in PNe.

scholarly journals New atomic data for trans-iron elements and their application to abundance determinations in planetary nebulae1This review is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

2011 ◽  
Vol 89 (4) ◽  
pp. 379-385 ◽  
Author(s):  
N.C. Sterling ◽  
M.C. Witthoeft ◽  
D.A. Esteves ◽  
R.C. Bilodeau ◽  
A.L.D. Kilcoyne ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Cross Sections ◽  
Dielectronic Recombination ◽  
Elemental Abundance ◽  
Oscillator Strengths ◽  
Rate Coefficients ◽  
Atomic Data ◽  
Element Abundance ◽  
International Colloquium ◽  
Stellar Spectra

Investigations of neutron(n)-capture element nucleosynthesis and chemical evolution have largely been based on stellar spectroscopy. However, the recent detection of these elements in several planetary nebulae (PNe) indicates that nebular spectroscopy is a promising new tool for such studies. In PNe, n-capture element abundance determinations reveal details of s-process nucleosynthesis and convective mixing in evolved low-mass stars, as well as the chemical evolution of elements that cannot be detected in stellar spectra. Only one or two ions of a given trans-iron element can typically be detected in individual nebulae. Elemental abundance determinations thus require corrections for the abundances of unobserved ions. Such corrections rely on the availability of atomic data for processes that control the ionization equilibrium of nebulae (e.g., photoionization cross sections and rate coefficients for various recombination processes). Until recently, these data were unknown for virtually all n-capture element ions. For the first six ions of Se, Kr, and Xe — the three most widely detected n-capture elements in PNe — we are calculating photoionization cross sections and radiative and dielectronic recombination rate coefficients using the multi-configuration Breit–Pauli atomic structure code AUTOSTRUCTURE. Charge transfer rate coefficients are being determined with a multichannel Landau–Zener code. To calibrate these calculations, we have measured absolute photoionization cross sections of Se and Xe ions at the Advanced Light Source synchrotron radiation facility. These atomic data can be incorporated into photoionization codes, which we will use to derive ionization corrections (hence abundances) for Se, Kr, and Xe in ionized nebulae. Using Monte Carlo simulations, we will investigate the effects of atomic data uncertainties on the derived abundances, illuminating the systems and atomic processes that require further analysis. These results are critical for honing nebular spectroscopy into a more effective tool for investigating the production and chemical evolution of trans-iron elements in the Universe.

scholarly journals New Radiative Atomic Data

2005 ◽  
Vol 13 ◽  
pp. 668-671
Author(s):  
Sultana N. Nahar
Keyword(s):  
Cross Sections ◽  
Transition Probabilities ◽  
Energy Levels ◽  
Radiative Transition ◽  
Dielectronic Recombination ◽  
Oscillator Strengths ◽  
Rate Coefficients ◽  
Atomic Data ◽  
Self Consistent ◽  
Ion Recombination

AbstractLarge amount of new radiative atomic data for I) energy levels, II) oscillator strengths (f), line strengths (S), radiative transition probabilities (A), III) photoioniztion cross sections (σPI) – total and level-specific, and IV) unified total and level-specific electron-ion recombination rate coefficients, αR, including radiative and dielectronic recombination (RR and DR) are reported for various astrophysical applications. Most of the data are with fine structure. These data are not yet available from any databases. Photoionization and recombination data are self-consistent, using the same wave-function for both processes.

scholarly journals Reactive collision of electrons with CO+ in cometary coma

2018 ◽  
Vol 615 ◽  
pp. A53 ◽  
Author(s):  
Y. Moulane ◽  
J. Zs. Mezei ◽  
V. Laporta ◽  
E. Jehin ◽  
Z. Benkhaldoun ◽  
...  
Keyword(s):  
Cross Sections ◽  
Vibrational Excitation ◽  
Dissociative Recombination ◽  
Molecular Data ◽  
Molecular Ions ◽  
Rate Coefficients ◽  
Nuclear Dynamics ◽  
Cometary Coma ◽  
Reactive Collisions ◽  
The Cross

Context. In order to improve our understanding of the kinetics of the cometary coma, theoretical studies of the major reactive collisions in these environments are needed. Deep in the collisional coma, inelastic collisions between thermal electrons and molecular ions result in recombination and vibrational excitation, the rates of these processes being particularly elevated due to the high charged particle densities in the inner region. Aims. This work addresses the dissociative recombination, vibrational excitation, and vibrational de-excitation of electrons with CO+ molecular cations. The aim of this study is to understand the importance of these reactive collisions in producing carbon and oxygen atoms in cometary activity. Methods. The cross-section calculations were based on multichannel quantum defect theory. The molecular data sets, used here to take into account the nuclear dynamics, were based on ab initio R-matrix approach. Results. The cross-sections for the dissociative recombination, vibrational excitation, and vibrational de-excitation processes, for the six lowest vibrational levels of CO+ – relevant for the electronic temperatures observed in comets – are computed, as well as their corresponding Maxwell rate coefficients. Moreover, final state distributions for different dissociation pathways are presented. Conclusions. Among all reactive collisions taking place between low-energy electrons and CO+, the dissociative recombination is the most important process at electronic temperatures characterizing the comets. We have shown that this process can be a major source of O(3P), O(1D), O(1S), C(3P) and C(1D) produced in the cometary coma at small cometocentric distances.

New Atomic Data for Astronomy: An Introductory Review

1995 ◽  
Vol 10 ◽  
pp. 570-571
Author(s):  
M.J. Seaton
Keyword(s):  
Line Profile ◽  
Cross Sections ◽  
Transition Probabilities ◽  
Energy Levels ◽  
Experimental Studies ◽  
Theoretical Work ◽  
Radiative Transition ◽  
Rate Coefficients ◽  
Atomic Data ◽  
Collisional Rate Coefficients

Astronomers require the following basic atomic data: energy levels and wavelengths’, radiative transition probabilities; cross sections for photo-ionisation and for collisional processes; and line profile parameters. They also require processed data such as: level populations; opacities; radiation forces; line emissivities; and collisional rate-coefficients.Many of the data used by astronomers come from theoretical work. Experimental work is of importance in determining accurate wavelengths, in providing essential checks on theory for radiative probabilities and collision rates, and in the determination of line-profile parameters. Experimental studies are particularly important for processes of collisional ionisation.

Rotational de-excitations of C3H+ (1Σ+) by collision with He: new ab initio potential energy surface and scattering calculations

2020 ◽  
Vol 494 (4) ◽  
pp. 5675-5681 ◽  
Author(s):  
Sanchit Chhabra ◽  
T J Dhilip Kumar
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Cross Sections ◽  
Energy Surface ◽  
Molecular Ions ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Collisional Rate Coefficients

ABSTRACT Molecular ions play an important role in the astrochemistry of interstellar and circumstellar media. C3H+ has been identified in the interstellar medium recently. A new potential energy surface of the C3H+–He van der Waals complex is computed using the ab initio explicitly correlated coupled cluster with the single, double and perturbative triple excitation [CCSD(T)-F12] method and the augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis set. The potential presents a well of 174.6 cm−1 in linear geometry towards the H end. Calculations of pure rotational excitation cross-sections of C3H+ by He are carried out using the exact quantum mechanical close-coupling approach. Cross-sections for transitions among the rotational levels of C3H+ are computed for energies up to 600 cm−1. The cross-sections are used to obtain the collisional rate coefficients for temperatures T ≤ 100 K. Along with laboratory experiments, the results obtained in this work may be very useful for astrophysical applications to understand hydrocarbon chemistry.

Inelastic scattering of interstellar silyl cyanide (SiH3CN) by helium atoms : cross-sections and rate coefficients for A- and E-SiH3CN

2021 ◽  
Vol 507 (4) ◽  
pp. 5264-5271
Author(s):  
Manel Naouai ◽  
Abdelhak Jrad ◽  
Ayda Badri ◽  
Faouzi Najar
Keyword(s):  
Inelastic Scattering ◽  
Total Energy ◽  
Cross Sections ◽  
Three Dimensional ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Explicitly Correlated ◽  
Correlation Consistent ◽  
Triple Excitation

ABSTRACT Rotational inelastic scattering of silyl cyanide (SiH3CN) molecule with helium (He) atoms is investigated. Three-dimensional potential energy surface (3D-PES) for the SiH3CN–He interacting system is carried out. The ab initio 3D-PES is computed using explicitly correlated coupled cluster approach with single, double, and perturbative triple excitation CCSD(T)-F12a connected to augmented-correlation consistent-polarized valence triple zeta Gaussian basis set. A global minimum at (R = 6.35 bohr; θ = 90○; ϕ = 60○) with a well depth of 52.99 cm−1 is pointed out. Inelastic rotational cross-sections are emphasized for the 22 first rotational levels for total energy up to 500 cm−1 via close coupling (CC) approach in the case of A-SiH3CN and for the 24 first rotational levels for total energy up to 100 cm−1 via CC and from 100 to 500 cm−1 via coupled states (CS) in the case of E-SiH3CN. Rate coefficients are derived for temperature until 80 K for both A- and E-SiH3CN–He systems. Propensity rules are obtained for |ΔJ| = 2 processes with broken parity for A-SiH3CN and for |ΔJ| = 2 processes with |ΔK| = 0 and unbroken parity for E-SiH3CN.

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