Electron impact ionization of atomic hydrogen

Abstract

cross Sections (TDCS) o f atomic hydrogen by electron impact ionization in the intermediate and high energy regimes. The prescription is particularly suitable for asymmetric geometry. TDCS results have been computed in the Ehrhardt geometry for incident energies 150 eV and 250 eV and ejected energies 5 eV and 3 eV with different fixed scattering angles of the faster electron. Excellent agreement is noted with the absolute measurements of Ehrhardt el 01.

Ionization of metastable H(2S) atom by electron and positron impact

“…(10) is similar to our earlier work [5], for the numerical evaluation of the present TDCS for ionization from 2S state, we had to face some convergence difficulty arising most probably due to the lower value of the initial bound-state parameter 2~ occurring in the exponential term exp [-~ir2 ] in the expression of r (r2). In order to circumvent this convergence problem we had to modify our previous [5] integrand occurring in the expression of the T matrix element. To clarify this point, we repeat the relevant steps of our earlier theory [5].…”

“…Recently we developed an approach to study electron and positron impact single ionization [5,6] of H(1S) atom for coplanar and asymmetric geometry and obtained very good agreement with experiment at intermediate and high energies. The salient feature of the approach was that the final-state wave function takes account of the correlation between the two outgoing particles and satisfies the three-body asymptotic boundary condition for asymmetric geometry (i.e.…”

“…In order to construct T~-in eq 9 (1) satisfying the incoming-wave boundary condition, we assume that the slower ejected electron is represented by a full Coulomb wave, while the faster scattered particle is treated in the framework of eikonal approximation 9 Thus in the present approach we have chosen the wave function Ti as (5) ~ = r where r represents the wave function for the ejected electron given by…”

“…In order to circumvent this convergence problem we had to modify our previous [5] integrand occurring in the expression of the T matrix element. To clarify this point, we repeat the relevant steps of our earlier theory [5].…”

“…In view of eqs. (13b) and (14), I0 can be rewritten as The contour integral in t occurring in (19) has been transformed [5] to a one-dimensional real integral ranging from 0 to a and then the final real two-dimensional integration in v and y (y being the transformed variable of t) is carried out numerically using Gauss-Legendre (for v) and Gauss-Laguerre (for y) quadrature methods. However, while carrying out the v integration for fLxed values of the other variable y, convergence problem arises in the v integration.…”