Indian J. Phys. 72B (I). 11-17 (1998) UP B — an international journal Studies on positron-hydrogen ionization cross sections A Bandyopadhyay1, P K Dutta2, K Roy1, P MandaPand N C Sil1 'Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Calcutta-7(X) 032, India. 'Department of Mathematics, Visva Bharati University, Santiniketan-731235. West Bengal, India Received 5 May 1997, aicepted i 7 November, 1997 Abstract : In this work, we report the results of the total ionization cross section of hydrogen atom by positron impact We also explore some interesting kineirtatical situations of the single and double differential cross sections for near future experiments In our calculation, we use the asymptotically correct final-state wave function which involves three apropriate confluent hypergeometnc functions We compare our total cross section values with the available theoretical results and the existing experimental data. Keywords . Ionization cross section, asymptotically correct final-state wave function, con - fluent hypergeometnc functions PACS Nos. 34 80 Dp, 34.50 Fa, 1. Introduction The study of scattering by positron impact alone has its own beauty. A number of highly interesting phenomena occurs when a stream of positron passes through a gas. Moreover, the positron being positively charged is distinguishable from the atomic or molecular electron. There is no electron exchange analogue for positron scattering and as such the total wave function need not be antisymmetrized. In recent years, considerable developments are made in the experimental findings of positron-atom scattering due to the availability of intense positron beams of required energy and sensitive detectors. New fast-counting techniques have made it possible to enlarge much further the base already established and have brought into practical possibility of measurement that seemed unattainable before. So studies on positron collision have now become a very interesting field. A spurt of activities is also noticed in the positron-induced ionization studies, because of the recent observations in the laboratory. The points of contact between theory and experiment are thus becoming close. Spicher et al [ 1 ] measured total ionization cross sections for atomic and moleculur hydrogen targets upto incident positron energies of 600 eV and compared their results with the available theoretical predictions [2-5]. However, the agreement between these theoretical © 1998 I ACS