Choosing Pseudostates in the Close-Coupling Formalism for the Electron—Atomic-Hydrogen System

Both elastic and inelastic scattering are studied in the framework of the close-coupling equations. The models are formulated in terms of integral equations for T matrices in momentum space. This representation enables one to study the effects of approximations to the multiple-scattering series in a direct manner. For elastic scattering we can thus establish that the approximations made in using a second-order optical-potential formalism give rise to at most a 10% error in the reaction mechanism at 50 eV and considerably less at higher energies. Inelastic Is-2s and Is-2p scattering is analysed in terms of a three-state close-coupling model and approximations to it.

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Electron capture in slow collisions of O6+ions with atomic hydrogen

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834922 ◽

2019 ◽

Vol 625 ◽

pp. A29

Author(s):

Xiaohe Lin ◽

Yong Wu ◽

J. G. Wang ◽

Bin Shao ◽

R. K. Janev

Keyword(s):

Electron Capture ◽

Cross Sections ◽

Ground State ◽

Atomic Hydrogen ◽

Theoretical Data ◽

Rate Coefficients ◽

Hydrogen Atoms ◽

Close Coupling ◽

Radiative Transitions ◽

Reaction Channels

Aims. Electron capture in collisions of highly charged O6+ions with ground-state hydrogen atoms is a very important process in solar wind X-ray studies.Methods. In the present study, the full quantum-mechanical molecular-orbital close-coupling method is employed to study electron capture reactions in collisions of O6+ion with ground-state atomic hydrogen in the energy region from 10−4keV u−1to 5 keV u−1. The ab initio multi-reference single- and double-excitation configuration interaction (MRD-CI) method is used to calculate the potential and coupling data used in the QMOCC calculations.Results. Total and state-selective cross sections for the dominant and subdominant reaction channels are calculated and compared with the available experimental and theoretical data. The branching ratios for Lithium-like O5+excited ions are used to calculate the contribution of cascade radiative transitions fromn = 5 levels to the population of 4l states. From the calculated cross sections, reaction rate coefficients are obtained for temperatures between 1000 and 1 × 109K and compared with other calculations.

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New and Old Measurements of Electron Scattering in Atomic Hydrogen

Australian Journal of Physics ◽

10.1071/p98023 ◽

1998 ◽

Vol 51 (4) ◽

pp. 633 ◽

Cited By ~ 6

Author(s):

J. F. Williams

Keyword(s):

Cross Section ◽

Cross Sections ◽

Differential Cross ◽

Atomic Hydrogen ◽

Intermediate Energy ◽

Absolute Calibration ◽

Absolute Cross Section ◽

Close Coupling ◽

R Matrix ◽

Correlation Parameters

A critical look is made of discrepancies and agreements between new and old measurements and theories for elastic and n = 2 excitation of atomic hydrogen by electron impact, mainly at 16·5, 54 and 100 eV. A discussion of earlier work indicates the contributions of Weigold and colleagues. The diffculties of observing and modelling small scattered fluxes at backward scattering angles and of making absolute cross section calibrations are noted. New measurements of elastic scattering at 16·5 eV confirm earlier measured angular distributions. An absolute calibration of the differential cross section at 16·5 eV gives agreement within one standard deviation with intermediate energy R-matrix and multi-pseudostate close coupling values. At 16·5 eV, measurements of the separate 2s and 2p differential cross sections and the lambda, R and I correlation parameters again support the values from those theories.

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