Excitation from metastable 23S states of helium by electrons and positrons

1996 ◽  
Vol 74 (7-8) ◽  
pp. 521-526 ◽  
Author(s):  
Surbhi Verma ◽  
Rajesh Srivastava
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Many Body ◽  
Many Body Theory ◽  
Electrons And Positrons ◽  
Body Theory ◽  
Orientation Parameters ◽  
Approximation Calculation

Our recent distorted-wave approximation calculation for the electron-impact excitation cross sections of the helium atom from its 23S state to upper states was extended to obtain alignment and orientation parameters for n3P (n = 2, 3, 4) excitations. Further, similar results are obtained by considering the excitation by impact of positrons. The calculated alignment and orientation results are compared with the only available theoretical electron-impact results obtained using first-order many-body theory.

Excitation of the 3D states of helium by electrons and positrons

1996 ◽  
Vol 74 (7-8) ◽  
pp. 509-517 ◽  
Author(s):  
Surbhi Verma ◽  
Rajesh Srivastava
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Ground State ◽  
Stokes Parameters ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Distorted Wave ◽  
Positron Impact ◽  
Wave Approximation ◽  
Electrons And Positrons

Distorted-wave approximation calculations were carried out for the electron-impact excitation of 31,3D states from the 11S ground state of helium. Results are presented at an electron energy of 40 eV for the Stokes parameters P1-P4; coherence parameters Pl, γ, [Formula: see text], ρ00; and differential cross sections where most other theoretical and experimental data are available for comparison. The calculation is further extended to the positron-impact 11S–31D excitation in helium and comparison with the corresponding electron-impact results is discussed.

Relativistic R-matrix close-coupling method based on the effective many-body Hamiltonian: electron-impact excitation of the 3s2 1S0–3s3p1P1o electric dipole-allowed transition of the Ar6+ ion1This article 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. 457-463
Author(s):  
Juan A. Santana ◽  
Yasuyuki Ishikawa
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Electric Dipole ◽  
Coupling Method ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Many Body ◽  
Close Coupling ◽  
R Matrix ◽  
Excitation Cross Sections

Electron-impact excitation cross sections of the electric dipole-allowed 3s2 1S0–3s3p [Formula: see text] transition in Mg-like argon (Ar6+) are calculated using the configuration-interaction and effective many-body Hamiltonian R-matrix close-coupling methods. The near-threshold electron-impact excitation cross sections computed with the effective many-body Hamiltonian R-matrix close-coupling method are in good agreement with the benchmark experimental results.

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