Resonance In Positron-Mg Scattering At Low Impact Energy

In recent years, positron-atom collision has simulated more and more scientific research. Great successes have been achieved both experimentally and theoretically, a number of predictions that cover almost all aspects of the positron-hydrogen system theoretical calculations have given successful(Igarashi and Toshima 1994, Kernoghan et al 1995, 1996, Mitroy and Stelbovics 1994, Ratnavelu et al 1996, Kuang and Gien 1997, Kadyrov A S and Bray I 2002, Zhou et al in press). However, as to the many-electron atoms scattering with positron, there remain obvious discrepancies between the experimental measurements and the theoretical predictions, for the various reaction within the complex collision system. Nowadays, with the remarkably improvement on the experimental technology, corresponding descriptions from the theory are expected urgently, which comes into being the great challenge to our theoretical workers.In the past 20 years, some theoretical models have been developed to the positron-atom collision, where in the common models include the distorted-wave Born approximation method (DWBA), the R-matrix method, the convergent close coupling method (CCC) and the coupled-channels optical potential method (CCO). The DWBA method are more valid for the collision in the high energy range; the R-matrix method, which was proposed by Burke, Noble and Scott, and then developed by the Belfast groups, is more suitable for the collision in the low energy range and when the incident energy reach to the intermediate range, a series of pseudo-structure are caused due to the use of the large number of pseudo-states; the CCC method has advantage over the simple target atom, for example, the H and H e , and there are some difficulty in treating the more complex target atoms. So it is necessary to develop a more common theory model, which can descript the positron collision with the many-electrons atom explicitly.The CCO method, developed in 1980's by McCarthy et al, has beenwidely applied to the electron scattered by various atoms and molecules and has achieved great success. In the recent year, Prof. Zhou Ya-jun et al have successfully developed the CCO method to the positron collision with atom H. In the present paper, we propose a complex, local polarization to represent the Positronium formation (Ps) arrangement channel and ionization continuum channel, and develop the CCO method to the positron collision with the complex atom.We use a complex, local polarization potential, develop the CCO-method to the researches of the collision between positron and complex atoms. In this paper, we calculate the resonance at low impact energy (below the threshold ), and get the results about the total and partial wave cross sections, locations of resonances at 3.88eV(S-wave),4.00eV-4.03eV(S,P,D-wave),4.250eV-4.275eV(S,P,D,F-wave),4.52eV(D,F-wave),4.81eV(P,F-wave), with simple analysis. We also calculate the cross sections when local polarization potential be considered , the result strengthen our result about the location of the resonances. So we believe our methods are feasible at low impact energy.