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 Brauner et al [8] and with the second Born calculation. © 1995 the Indian Academy of Sciences.

J N DAS

A DEY

K CHAKRABARTI

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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University Of Calcutta

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

Pramana

The triple differential cross section for electron impact ionisation of helium atoms has been calculated in the coplanar asymmetric geometry following the multiple scattering approach of Das. The method has already been successfully employed to describe the electron impact ionisation problem for the hydrogen atom. Here the impact energy of the incident electron is taken to be 150 and 250 eV in an intermediate energy range where there are still some discrepancies between theory and experiment. Present results are compared with the available experimental data and with two of the most recent calculations in some cases, and are found to be in reasonable accord with experiment, particularly in the binary peak region. The present calculation for 250 eV incident energy reproduces the experimental results in some cases better than other theories.

Fulltext

Australian Journal of Physics

MULTIPLE-SCATTERING CALCULATION FOR IONIZATION OF HELIUM-ATOMS BY ELECTRONS AT INTERMEDIATE ENERGIES

Triple-differential cross sections for ionization of hydrogen atoms by electrons have been calculated both for small- as well as large-momentum-transfer cases at intermediate (5I0-20I0) and high (20I0) energies (I0 being the ionization potential) following a method which uses a final-channel three-particle wave function determined by one of the authors. This wave function resulted from an analysis of the three-particle wave equation in momentum space and is correct to the first order in the interaction potentials. Incidentally, it is also the first-order Faddeev wave function. The wave function has been suitably normalized before it is used. The computed results are generally good. The small-momentum-transfer results are in nice agreement with the experimental data except for a certain angular region which includes the recoil peak. The domain over which the present results agree in trend with the experimental measurements is somewhat larger than that for the distorted-wave-Born-approximation calculation. Large-momentum-transfer results are also in qualitative agreement with experiments. There are indications that quantitatively the present results may be better there. Total-ionization cross-section results are also in excellent agreement with experiment above 200-eV energy. These facts together with the simplicity of the calculation establish that the present method has certain advantages over other existing methods. The present calculation may be the starting point for a more elaborate calculation which will take into account more accurately the correlation and higher-order effects in the final-channel three-particle wave function. © 1993 The American Physical Society.

Physical Review A

Electron-hydrogen-atom ionization collisions at intermediate (5I0-20I0) and high (20I0) energies

Triple differential cross-sections for ionization of hydrogen atoms by electrons and positrons have been calculated for symmetric coplanar geometry following a multiple scattering method suggested and used earlier by the authors. Results show single binary peaks exactly at 45° and double binary peaks exactly at 135° for higher energies as are expected from an analysis of Briggs [3]. At lower energies there are certain deviations from these values. An analysis of scattering mechanism at peaks are also given. This supports Briggs' explanation. © 1993 Indian Academy of Sciences.

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ISSN	0304-4289