Positron scattering from atomic sodium

Abstract

Close-coupling calculations of positron scattering from atomic sodium are performed from threshold to 100 eV. The alkali atom is represented by a frozen-core model based upon the Hartree-Fock approximation. The close-coupling calculations are performed in a model containing multiple sodium (3s, 3p, 4s, 3d, 4p) and positronium states (1s, 2s, 2p, 3s, 3p, 3d). Subsidiary calculations with three and ten positronium states were performed at selected energies to test the convergence of the positronium formation cross section. The predicted total cross sections agree with the experimental data of Kwan et al but there are differences with the data of Kauppila et al. The net positronium formation cross section underestimates the experimental data of Zhou et al.

Threshold behavior of positronium formation in positron–alkali-metal scattering

“…There are several theoretical studies of positron scattering from alkali targets at energies above 1 eV [15][16][17][18][19][20][21], where they could be tested against experiment [22][23][24]. Threshold behavior in positron scattering from lithium was studied in Refs.…”

Positronium formation for e+-Na scattering at low and intermediate energies

“…The present cross sections are shown with the HSCC cross section [1] and the experimental measurements [2]. The previous CC calculations [3,4] are also shown. The present results seems to be in good agreement with the measured data at energy above 1 eV.…”

“…There is no question that the positronium(Ps) channel gives a very significant effect on the positronsodium(Na) scattering system [1][2][3][4] at low and intermediate energies. In the earlier calculations [5][6][7][8], the close-coupling equations have been used to treat this system by excluding the possibility of Ps formation.…”

“…This motivated the realistic close-coupling calculations which explicitly included the Ps channels [10][11][12]. Walters and co-workers [4,13] as well as Ryzhikh and Mitroy [3], working independently, predicted that the Ps formation cross section will rapidly diminish as the incident energy decreases. The prediction was experimentally [2] verified for Li but not for Na.…”

Time-dependent Approach to Positron - Hydrogen Scattering

“…Nevertheless, nearly all reported theoretical studies of electron/positron scattering from atoms utilise a time-independent approach. For example, the convergent-close-coupling method (Bray andStelbovics 1995, 1997;Ryzhikh and Mitroy 1997), the distorted-wave Born approximation method Wang et al . 1995), the convergent R-matrix method (Bartschat et al .…”