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Journal ArticleDOI

Triple differential cross sections for ionization of hydrogen atoms by positrons in a Schwinger variational calculation

01 Jul 1995-Pramana (Springer India)-Vol. 45, Iss: 1, pp 41-46
TL;DR: Schwinger variational principle has been used to calculate triple differential cross-sections for ionization of hydrogen atoms by positrons at intermediate and high energies for Ehrhardt type asymmetric geometry.
Abstract: Schwinger variational principle has been used to calculate triple differential cross-sections for ionization of hydrogen atoms by positrons at intermediate and high energies for Ehrhardt type asymmetric geometry The results agree in general with the calculations of Brauneret al [8] and with the second Born calculation
Citations
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Journal ArticleDOI
01 Apr 2001-Pramana
TL;DR: In this paper, low energy positron impact ionization of atomic hydrogen is studied theoretically using the hyperspherical partial wave method of Das in constant Θ12, equal energy sharing geometry.
Abstract: Low energy positron impact ionization of atomic hydrogen is studies theoretically using the hyperspherical partial wave method of Das [1] in constant Θ12, equal energy sharing geometry. The TDCS reveal considerable differences in physics compared to electron impact ionization under the same geometry.

1 citations

Journal ArticleDOI
01 Mar 2002-Pramana
TL;DR: Schwinger variational principle is used here to study large momentum transfer cases of electron and positron impact ionization of atomic hydrogen from the ground state at intermediate and moderately high energies.
Abstract: Schwinger variational principle is used here to study large momentum transfer cases of electron and positron impact ionization of atomic hydrogen from the ground state at intermediate and moderately high energies. The results appear somewhat better compared to other theories.

1 citations

References
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Book
01 Feb 1984

1,037 citations

Journal ArticleDOI
TL;DR: In this article, the triple differential cross section for the ionisation of atomic hydrogen by fast electrons is analyzed in a coplanar, asymmetric geometry by using the second Born approximation, and the authors find that the binary peak is shifted to larger angles relative to the first Born result and is reduced in magnitude.
Abstract: The triple differential cross section for the ionisation of atomic hydrogen by fast electrons is analysed in a coplanar, asymmetric geometry by using the second Born approximation. The authors find that the binary peak is shifted to larger angles relative to the first Born result and is reduced in magnitude. The recoil peak exhibits a major enhancement and is also shifted towards large angles.

72 citations

Journal ArticleDOI
TL;DR: Differential cross sections have been measured for the electron-impact ionization of atomic hydrogen, using the ($e, $2e$) technique with coplanar asymmetric kinematics.
Abstract: Differential cross sections have been measured for the electron-impact ionization of atomic hydrogen, using the ($e$, $2e$) technique with coplanar asymmetric kinematics. The experiments were performed at an incident energy of 250 eV with the slow outgoing electron being detected at energies of 5, 10, and 14 eV, for scattering angles of the fast outgoing electron of 3\ifmmode^\circ\else\textdegree\fi{}, 5\ifmmode^\circ\else\textdegree\fi{}, and 8\ifmmode^\circ\else\textdegree\fi{}. The data are compared with differential cross sections calculated with use of the factorized distorted-wave impulse approximation, the plane-wave impulse approximation, and three recent Born-approximation calculations, consisting of first-order Born, second-order Born, and eikonal Born series treatments. In the distorted-wave impulse approximation calculations we investigate the effect of using different descriptions for the fast outgoing electron. Comparison of the data and the calculated cross sections indicates reasonable agreement with the distorted-wave impulse calculations, and good agreement with the second-order and eikonal Born series calculations.

59 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured the positron impact ionisation cross section, sigma ion+, and positronium (Ps) formation cross section from their thresholds up to energies where sigma ions merges with the electron impact ionization cross section and sigma ps is negligible.
Abstract: The authors measure the positron impact ionisation cross section, sigma ion+, and the positronium (Ps) formation cross section, sigma Ps, from their thresholds up to energies where sigma ion+ merges with the electron impact ionisation cross section, sigma ion-, and sigma Ps is negligible. The maximum values are 1.7*10-16 cm2 for sigma ion+ around 63 eV (as compared with 1.1*10-16 cm2 for sigma ion- near 65 eV) and 2.3*10-16 cm2 for sigma ps, around 20 eV. Above 120 eV the measurements of sigma Ps are consistent with zero. Above 250 eV sigma ion+ and sigma ion- are equal within the experimental errors. At intermediate energies sigma ion+ exceeds sigma ion- whereas near threshold sigma ion+< sigma ion-, a fact which is qualitatively in accordance with the Wannier theory of threshold behaviour. The authors' data, together with literature values for the positron total scattering cross section, give evidence for a structure in the elastic cross section at the Ps-formation threshold.

55 citations

Journal ArticleDOI
TL;DR: In this paper, the triple differential cross section for the ionization of atomic hydrogen by fast electrons is analyzed in the case of a coplanar, asymmetric geometry by using the eikonal Born series theory.

47 citations