Algebraic coupled-state calculation of positron-hydrogen collisions at low energy, using large coupling schemes

Kuang, Yu Rang (1996) Algebraic coupled-state calculation of positron-hydrogen collisions at low energy, using large coupling schemes. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The Harris-Nesbet algebraic approach is employed to carry out calculations of positron-hydrogen scattering at energy below the first excitation threshold of the hydrogen atom. The main work of this thesis is to extend the Harris-Nesbet method to large scale coupled-state calculations. With coupling schemes composed of lower physical states: 1s, 2s, 2p of both hydrogen and positronium, and a pseudo 3p of hydrogen associated with a number of short ranged correlation functions, calculations for positron-hydrogen scattering are accurately carried out for seven partial waves from L=0 to 6. Comparison with available theoretical results shows that good agreement is obtained at energies considered. Our total elastic and total Ps formation cross sections are also in good agreement with existing accurate theoretical results. Our total Ps formation and integrated cross section (total elastic plus total Ps formation) agree with available experimental data. The scattering length obtained also agree well with the existing theoretical values. There are three, two and one resonances observed for the S-, P- and D-waves below the first excitation threshold of hydrogen, respectively, which confirms the existing observations. -- On the other hand, we also carry out calculations for an 18-state and a 20-state coupling schemes. Both sets of results show reasonable agreement with each other and available findings.

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