Relativistic (e, 2e) collisions on atomic inner shells in symmetric geometry

Abstract

Abstract. We report here on an (e, 2e) experiment at relativistic electron energies (Eo = 300 keV and 500 keV) in coplanar symmetric geometry. Absolute triple differential cross section measurements for K-shell ionisation of gold, silver and copper are compared with a number of simple first order approximations. Appreciable discrepancies between theory and experiment are found, which reduce with decreasing Z and increasing primary energy. The theoretical calculations show that spin flip effects are important in symmetric geometry, in earlier works these had been neglected.

Theoretical analysis of the relativistic first order Born approximation for inner shell (e, 2e) processes

“…In coplanar symmetric geometry, a systematic experimental study of the impact energy and charge dependence of the TDCS has been carried out [3,4], the results of which are given in Fig. 2.…”

“…1a we compare a set of experimental data obtained with a gold target with results of the exact (this is, fully relativistic) first order Born theory of Sect. 2, two approximations to this theory [4,6], the Coulomb-Born theory of Jakubaßa-Amundsen [9,10] which employs nonrelativistic Coulomb scattering waves times a free electron spinor to represent all unbound electrons, and the rDWBA [13,14] where exact numerical solutions of the Dirac equation with an effective atomic potential are used. There exist drastic discrepancies in absolute magnitude between the relativistic and semirelativistic first order Born results.…”

“…If the ejected electron state is, for whatever reason, represented by an approximate one particle wave function, this property will in general be lost. In particular, this is the case for the various types of semirelativistic scattering wave functions used in the previous studies of the Born matrix elements [4,6,9,10] if the bound state wave function carries the correct four spinor structure [9]. From (3a), one then formally again encounters additional one body potential matrix elements of the type discussed above.…”

“…Therefore quite naturally, the first studies of relativistic (e, 2e) processes considered relativistic extensions of this work [4,6,9,10]. However in all these studies semirelativistic wave functions were used.…”

“…For a number of years, substantial discrepancies existed between the absolute experimental data for triple differential cross sections (TDCS) for electron impact ionization of inner shells of high-Z atoms obtained by Nakel and collaborators [1][2][3][4][5] and the results of theoretical calculations of these processes [4,[6][7][8][9][10][11][12]. However recently, definite progress towards quantitative agreement between theory and experiment could be achieved with the implementation of a fully relativistic distorted wave Born approximation (rDWBA) [13][14][15].…”