The use of basis splines and non-orthogonal orbitals in<i>R</i>-matrix calculations: application to Li photoionization

Zatsarinny, Oleg; Fischer, Charlotte Froese

doi:10.1088/0953-4075/33/3/303

Cited by 94 publications

(60 citation statements)

References 54 publications

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“…Computer memory limitations often lead to the use of inconsistent sets of N-electron and (N + 1)-electron configurations. We note the existence of methods that may allow this problem to be avoided or its effects drastically reduced, in particular the method developed by Gorczyca et al (1995) and the B-spline R-matrix approach with non-orthogonal orbitals (e.g., Zatsarinny & Froese Fischer 2000;Zatsarinny & Tayal 2001), a code for which was recently published by Zatsarinny (2006). With this in mind, we chose consistent N-and (N + 1)-electron configurations for our calculations.…”

Section: Calculationsmentioning

confidence: 99%

Electron-impact excitation of neutral oxygen

Barklem¹

2006

A&A

105

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Aims. Our goal was to calculate transition rates from ground and excited states in neutral oxygen atoms due to electron collisions for non-LTE modelling of oxygen in late-type stellar atmospheres, thus enabling the reliable interpretation of oxygen lines in stellar spectra. Methods. A 38-state R-matrix calculation in LS -coupling has been performed. Basis orbitals from the literature are adopted, and a large set of configurations are included to obtain good representations of the target wave functions. Rate coefficients are calculated by averaging over a Maxwellian velocity distribution. Results. Estimates for the cross sections and rate coefficients are presented for transitions between the seven lowest LS states of neutral oxygen. The cross sections for excitation from the ground state compare well with existing experimental and recent theoretical results.

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Section: Calculationsmentioning

confidence: 99%

Electron-impact excitation of neutral oxygen

Barklem¹

2006

A&A

105

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“…The nonorthogonal orbitals provide much greater flexibility in the choice of wave functions than the orthogonal orbitals, and also allow the inclusion of correlation with a reasonable number of configurations and correlated orbitals ( Zatsarinny & Tayal 2001). Our calculations are performed using the multiconfiguration Hartree-Fock ( MCHF) method (Froese Fischer 1991;Zatsarinny & Froese Fischer 1999, 2000. In the MCHF approach the atomic state is represented by an atomic state function…”

Section: Target Levels Descriptionmentioning

confidence: 99%

Collision Strengths for Electron Scattering from Siii

Tayal

2008

Astrophysical Journal Supplement Series, The

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Electron impact excitation collision strengths and rates for transitions between fine-structure levels of the 3s 2 np (n ¼ 3 Y6), 3s3p 2 , 3s 2 ns (n ¼ 4Y 6), 3s 2 nd (n ¼ 3 Y5), 3s 2 nf (n ¼ 4 Y5), and 3s3p3d configurations in Si ii are calculated by using the Breit-Pauli B-spline R-matrix approach. The 31 target levels have been included in the closecoupling expansion in our collision calculation. The multiconfiguration Hartree-Fock method with term-dependent nonorthogonal orbitals is employed for an accurate representation of the target wave functions. The target levels have been described by using both spectroscopic and correlation radial functions. The atomic wave functions yield excitation energies that are in excellent agreement with experiment and other reliable calculations. The relativistic corrections are included through the one-body mass correction, Darwin, and spin-orbit operators in the Breit-Pauli Hamiltonian. The effective collision strengths have been calculated by integrating total resonant and nonresonant collision strengths over a Maxwellian distribution of electron energies, and these are presented over a wide temperature range suitable for modeling of astrophysical plasmas. Significant differences are noted with the previous eight-state R-matrix calculation, particularly for transitions involving higher excitation levels.

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“…The B-spline R-matrix approach (Zatsarinny & Froese Fischer 2000;Zatsarinny & Tayal 2001a) has been employed in collision calculations. In this method the nonorthogonal orbitals are used for the description of both the bound target state wave functions and the continuum scattering wave functions.…”

Section: Computational Detailsmentioning

confidence: 99%

Electron Collisional Excitation Rates for O i Using the B ‐Spline R ‐Matrix Approach

Zatsarinny

Tayal

2003

ASTROPHYS J SUPPL S

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The B-spline R-matrix approach has been used to calculate electron collisional excitation strengths and rates for transitions between the 3 P, 1 D, and 1 S states of ground configuration and from these states to the states of the excited 2s 2 2p 3 ns (n ¼ 3 5), 2s 2 2p 3 np (n ¼ 3 4), 2s 2 2p 3 nd (n ¼ 3 4), 2s 2 2p 3 4f , and 2s2p 5 configurations. The nonorthogonal orbitals are used for an accurate description of both the target wave functions and the R-matrix basis functions. The thermally averaged collision strengths are obtained from the collision strengths by integrating over a Maxwellian velocity distribution of electron energies, and these are tabulated over a temperature range from 1000 to 60,000 K. The parametric functions of scaled energy have also been obtained to represent collision strengths over a wide energy range or thermally averaged collision strengths at any desired temperature.

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The use of basis splines and non-orthogonal orbitals inR-matrix calculations: application to Li photoionization

Cited by 94 publications

References 54 publications

Electron-impact excitation of neutral oxygen

Electron-impact excitation of neutral oxygen

Collision Strengths for Electron Scattering from Siii

Electron Collisional Excitation Rates for O i Using the B ‐Spline R ‐Matrix Approach

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