Positronium formation in positron-helium scattering

Khan, Pritikana; Ghosh, Arnab

doi:10.1103/physreva.28.2181

Cited by 36 publications

(8 citation statements)

References 9 publications

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“…This is evidence that coupling via the continuum substantially enhances the capture process to excited states. The presence of a sharp dip in the differential cross section (figures 3 and 4) for both the eikonal (post and prior) models at an angle near 40" has also been predicted by the DWPO theory (Khan and Ghosh 1983a) and by the second Born theory (Basu and Ghosh 1988). This is somewhat unusual in that one might expect higher order terms in the Born series to smooth out such a sharp structure.…”

Section: Resultssupporting

confidence: 55%

“…Simple target wavefunctions, such as the single-zeta function of Fromme et a/ (1990), are acceptable approximations for intermediate energies so long as they contain the correct binding energy and reproduce the tail of the electron density. This being the case, the total cross sections are rather insensitive to the precise form of the wavefunction (Hewitt et a/ 1992, Khan and Ghosh 1983b).…”

Section: Positron-helium Scatteringmentioning

confidence: 99%

“…Results for collisions with a helium target are given in table 2 and figure 5. We have included the close-coupling results of Hewitt et al (1992) along with some data for the DWW approximation (Khan and Ghosh 1983b). We also include our Born calculation to give an idea of the effects of our approximations for the target atom.…”

Section: A8-(zt/u)mentioning

confidence: 99%

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Positronium formation in positron-atom collisions at intermediate energies

Bransden

Joachain

McCann

1992

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

187

254

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The formation of ground-state positronium in collisions of positrons with hydrogen and helium atoms is considered within the distorted-wave Born approximation. In particular the authors analyse the eikonal and continuum-distorted-wave models in both their post and prior forms. Differential and total cross sections are calculated over a broad range of intermediate energies extending from 40 to 500 eV. The results confirm that the total cross section decreases rapidly with increasing energy, as predicted by the simple first Born approximation, and do not agree with experimental evidence of a slower decay. The computed total cross sections for helium targets agree with those of the close-coupling model for energies above 100 eV. Below 100 eV the authors find a large post-prior discrepancy. The calculated differential cross sections show evidence of a Thomas peak at high energies for the CDW models but not for the eikonal models.

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Section: Resultssupporting

confidence: 55%

Section: Positron-helium Scatteringmentioning

confidence: 99%

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Positronium formation in positron-atom collisions at intermediate energies

Bransden

Joachain

McCann

1992

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

187

254

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“…formation in helium. Included in this figure are the first Born (FBA) and distorted wave (DwA) approximations of Mandal el a l (1979), the distorted wave polarized orbital (DWPO) method of Khan and Ghosh (1983), the second Born approximation of Deb et a/ ( D M S ) (1987a) and the classical trajectory Monte Carlo (CTMC) treatment of Schultz and Olson (1988). At collision velocities from just above threshold to about the peak, the distorted wave treatments show reasonable agreement with experiment, but at higher velocity, all the methods underestimate the measurements.…”

Section: Charge Transfermentioning

confidence: 99%

Recent advances in the comparison of matter- and antimatter-atom collisions

Schultz¹,

Olson²,

Reinhold³

1991

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

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The relatively recent advent of low energy antimatter projectiles has spurred a rapid advance in the comparison of matter-and antimatter-atom collisions. These experimental studies have in turn stimulated a great deal of theoretical effort to explain their results, and together both theory and experiment have shed new light on the dynamics of ion-atom collisions. Here we review these developments with particular emphasis on the processes of ionization and charge transfer. measurements, with those of Stein el al (1978), Kauppila el nl (1977) and Milloy and Crompton (1977).

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“…Figure 4 shows the present results (solid line) for the helium atomic target, displayed together with the DWA (dot-dashed curve from ref. [14]) and the CC (dashed curve from ref. [2]) calculations.…”

mentioning

confidence: 99%