Superelastic electron scattering from potassium

Stockman, K A; Karaganov, V.; Bray, Igor; Teubner, P. J. O.

doi:10.1088/0953-4075/31/20/004

Cited by 21 publications

(15 citation statements)

References 18 publications

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“…The e+K system has been considered previously (Stockman et al 1998(Stockman et al , 1999(Stockman et al , 2001, which demonstrated the applicability of the CCC approach to the collision system at all energies.…”

Section: Convergent Close Coupling Methodsmentioning

confidence: 99%

Non-LTE analysis of K I in late-type stars

Reggiani

Amarsi

Lind

et al. 2019

A&A

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Context. Older models of Galactic chemical evolution (GCE) predict [K/Fe] ratios as much as 1 dex lower than those inferred from stellar observations. Abundances of potassium are mainly based on analyses of the 7698 Å resonance line, and the discrepancy between GCE models and observations is in part caused by the assumption of local thermodynamic equilibrium (LTE) in spectroscopic analyses. Aims. We study the statistical equilibrium of K i, focusing on the non-LTE effects on the 7698 Å line. We aim to determine how non-LTE abundances of potassium can improve the analysis of its chemical evolution, and help to constrain the yields of GCE models. Methods. We construct a new model K i atom that employs the most up-to-date atomic data. In particular, we calculate and present inelastic e+K collisional excitation cross-sections from the convergent close-coupling (CCC) and the B-Spline R-matrix (BSR) methods, and H+K collisions from the two-electron model (LCAO). We constructed a fine, extended grid of non-LTE abundance corrections based on 1D MARCS models that span 4000 < T eff /K < 8000, 0.50 < log g < 5.00, −5.00 < [Fe/H] < +0.50, and applied the corrections to potassium abundances extracted from the literature. Results. In concordance with previous studies, we find severe non-LTE effects in the 7698 Å line. The line is stronger in non-LTE and the abundance corrections can reach ∼ −0.7 dex for solar-metallicity stars such as Procyon. We determine potassium abundances in six benchmark stars, and obtain consistent results from different optical lines. We explore the effects of atmospheric inhomogeneity by computing for the first time a full 3D non-LTE stellar spectrum of K i lines for a test star. We find that 3D modeling is necessary to predict a correct shape of the resonance 7698Å line, but the line strength is similar to that found in 1D non-LTE. Conclusions. Our non-LTE abundance corrections reduce the scatter and change the cosmic trends of literature potassium abundances. In the regime [Fe/H] −1.0 the non-LTE abundances show a good agreement with the GCE model with yields from rotating massive stars. The reduced scatter of the non-LTE corrected abundances of a sample of solar twins shows that line-by-line differential analysis techniques cannot fully compensate for systematic LTE modelling errors; the scatter introduced by such errors introduces a spurious dispersion to K evolution.

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Section: Convergent Close Coupling Methodsmentioning

confidence: 99%

Non-LTE analysis of K I in late-type stars

Reggiani

Amarsi

Lind

et al. 2019

A&A

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“…Further investigations of this transition have been performed using unpolarized electrons (Scholten et al 1988, Teubner et al 1990, Farrell et al 1989, Sang et al 1994 and polarized electron beams (Hanne et al 1982, McClelland et al 1985, 1986a, b, 1987, 1989, Hedgemann et al 1991, Scholten et al 1991. ACPs for ground to excited state transitions in other alkali metals, Li (Karaganov et al 1996(Karaganov et al , 1998, K (Stockman et al 1998) and Rb (Hall et al 1999), as well as for other targets including Ba (Register et al 1978, Zetner et al 1993, Li and Zetner 1994b, Cr (Hanne et al 1993), Yb (Li and Zetner 1994a) and Ca (Law and Teubner 1995) were measured using this method. This substantial body of experimental data has stimulated the development of sophisticated theoretical models with very close agreement between theory and experiment being attained for the lighter alkalis in particular.…”

Section: Introductionmentioning

confidence: 99%

Atomic collision parameters for electron de-excitation of the 4S-3P transition of sodium

Shurgalin

Murray

MacGillivray

et al. 1999

J. Phys. B: At. Mol. Opt. Phys.

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A comparison of measured Stokes parameters and atomic collision parameters (P lin , γ, L ⊥ , P +) is made for the excitation and de-excitation of the 3S-3P and 4S-3P transitions of Na respectively, for electrons with incident energies of 22, 30 and 50 eV. These parameters are obtained from 'time-inverse' experiments in which electrons are either superelastically (3P-3S) or inelastically (3P-4S) scattered from the laser prepared 3P state. The data are compared with calculations from a convergent close coupling (CCC) model and a second-order distorted wave Born (DWB2) model. Both models demonstrate very good agreement for 3S-3P transitions. For the 4S-3P transitions, the DWB2 is in better accord with experiment than the CCC for the P lin parameter, the CCC is in excellent agreement with experiment for γ and L ⊥ , and neither is in accord with experiment for P + .

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“…Alkali atoms such as Li and Na are easier to prepare in the laboratory, and yet their chemistry is very similar to that of H, having just one valence electron. This allowed for some very accurate measurements of e-Li [6][7][8], e-Na [9][10][11][12], and e-K [13][14][15] scattering systems. So the next stage in trying to understand the discrepancy for the e-H system was to extend the CCC method to the alkali atoms.…”

Section: Introductionmentioning

confidence: 99%

Taking the Convergent Close-Coupling Method beyond Helium: The Utility of the Hartree-Fock Theory

Bray

Weber

Fursa

et al. 2022

Atoms

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The convergent close-coupling (CCC) method was initially developed to describe electron scattering on atomic hydrogen and the hydrogenic ions such as He+. The latter allows implementation of double photoionization (DPI) of the helium atom. For more complex single valence-electron atomic and ionic targets, the direct and exchange interaction with the inner electron core needs to be taken into account. For this purpose, the Hartree-Fock (HF) computer codes developed in the group of Miron Amusia have been adapted. In this brief review article, we demonstrate the utility of the HF technique by examples of electron scattering on Li and the DPI of the H− and Li− ions. We also discuss that modern-day computer infrastructure allows the associated CCC code, and others, to be readily run directly via the Atomic, Molecular and Optical Science Gateway.

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Superelastic electron scattering from potassium

Cited by 21 publications

References 18 publications

Non-LTE analysis of K I in late-type stars

Non-LTE analysis of K I in late-type stars

Atomic collision parameters for electron de-excitation of the 4S-3P transition of sodium

Taking the Convergent Close-Coupling Method beyond Helium: The Utility of the Hartree-Fock Theory

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