Effect Of Polarization In (e,2e) Ionization

In recent years, a number of new directions have been pursed in (e,2e)investigations of election-impact ionization processes. Much attention has beenconcentrated on atomic outer shells, particularly with simple targets. Because of thesmallness of the cross section the core region has been the subject of fewer studies.The dynamical studies of inner-shell ionization in neon, argon [68,51,70] and xenon[79] revealed a number of interesting features of the scattering which weredistinctly different to outer-shell ionization. Developed in 1990's, the distorted wave Born approximation (DWBA) methodwhich deal with the problem of three bodies of interaction in the collision betweenelectron and atom provide the theoretical criterion to calculate the triple differentialcross section (TDCS) of the (e,2e) reaction. Recently, a series of experiment results[69, 70, 84, 85]were reported for (e,2e) ionization of the argon 2p and 3s orbital in ahighly asymmetric geometry. These experimental measurements show that thetheoretical treatments using the DWBA method have significant differencescomparing with experimental data in the overall shape and magnitude of the triple iv吉林大学博士学位论文differential cross section. The recoil-to-binary ratio is significantly underestimatedby the DWBA calculations；The standard DWBA calculations are approximatelysymmetric about the direction of momentum transfer ± k , while the experiment isclearly not；The calculated binary and recoil peaks show no structure where theexperiments might possibly show some. All of these differences present asubstantial challenge to theory. The differences between them show that a newdynamical mechanism may be necessary to explain the experimental data. To carry out detailed theoretical investigations of electron-atom collisionsrequires an accurate representation of the full projectile-target interaction thatconsists primarily of static, exchange and polarization contributions. The static andexchange contributions have been included in the DWBA method, the significantdifferences between the theoretical and experimental results indicate that thereexists a kinematic regime where the inclusion of the distorting effects is notsufficient to explain the differences between theoretical and experimental results.Therefore, we modified the DWBA calculations by introducing polarizationinteraction into the distorted potential of DWBA to test for the significance ofpolarization. Two different types of polarization potentials are introduced in the calculationsof TDCS. Firstly, we introduce a polarization via the density-functional theory innear-target region. In the outermost asymptotic region, the asymptotic form of theadiabatic polarization potential is adopted. Secondly, we include the polarizationinteraction by an optical model potential V~ , the influence of the non-treatedreaction channels is included in the complex polarization W . Then we calculate thepolarization W in the momentum-space and transform it to coordinate space to v吉林大学博士学位论文recalculate the distorted waves and TDCS of argon atom. We aim at showing the influence of polarization potential on the calculatedTDCS of inner shells for argon. In order to test the validity of our model, wecalculate the TDCS for argon 2p and 3s orbital in coplanar asymmetric geometry.Results of these calculations are compared with the data of the standard DWBA andexperiment. We have calculated the TDCS of Ar(2p) in a coplanar highly asymmetricgeometry, the impact energies are 8256 eV ,5720 eV and the slow ejected energyare 7eV ,10eV. In the present calculations, the polar angles of the fast electron aresettled at θf = 1.5o and θf = 0.5o respectively. The variable parameter is the polarangle θs of the ejected electron, which is scanned from 0o to 360o. This is theconvention adopted by Stefani et al and T...