Abstract
The inelastic scattering of positrons by excited lithium alkali atoms Li*(2p) have been investigated within the frame work of the coupled-static and frozen-core approximations with the assumption that the elastic and rearrangement channels are open. In the present work, a rather complicated computer code is developed based on the coupled-static, frozen-core and Green’s function partial wave expansion technique. The partial and total elastic and positronium (Ps) formation cross sections of e+-Li*(2p) are calculated through a wide range of incident energy of positrons ranging from 0.3 eV to 1000 eV. Also, we have calculated the partial and total elastic and rearrangement (reversal of the Ps formation) cross sections of Ps-Li+ collisions through the low, intermediate and high energy regions. The effect of polarization potential of the Ps atom is taken into our consideration. The total cross sections which corresponding to twelve partial cross sections (calculated at twelve values of the total angular momentum l = 0 to l = 11) are calculated for each channel. Our calculated total positronium formation cross sections are compared with experimental results and those calculated by other authors. The present calculations encourage the experimental physicists to carry out positron-lithium experiments by taking the excited lithium target into accounts in order to obtain more positronium especially in the low and intermediate energy regions.
Highlights
The importance of the study of positron-alkali atom collisions is the possibility of positronium (Ps) formation even at zero incident energy
The hyperspherical hidden crossing method (HHCM) is used to calculate the Ps formation cross section for positron-lithium collisions in the energy range 0 1.8 eV [2] as well as a correction term which includes the core polarization term in the model potential is added to the HHCM in the low-energy e Li scattering [3]
This paper presents a trial to investigate the effect of the excited state of the target on the production of Ps formation through the inelastic collisions of positrons with initially excited lithium atoms
Summary
The importance of the study of positron-alkali atom collisions is the possibility of positronium (Ps) formation even at zero incident energy. The positronium formation cross sections for the collision of positrons with lithium and sodium atoms are investigated using the hyperspherical close-coupling method [1] through the energy range 0.01 eV - 20 eV. The hyperspherical hidden crossing method (HHCM) is used to calculate the Ps formation cross section for positron-lithium collisions in the energy range 0 1.8 eV [2] as well as a correction term which includes the core polarization term in the model potential is added to the HHCM in the low-energy e Li scattering [3].
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