Theoretical study of electron capture process in heavy ion induced M shell ionization

The number of studies in M-shell ionization is considerably low compared to the other two shells i.e., K and L shell. Apart from direct coulomb ionization, simultaneous multiple ionization in higher shells and electron capture in the K and L shell of the projectile from target M shell may be significant in case of M-shell ionization. Here we have considered the initial electron capture cross-section formulation of K-shell electron capture from Nikolaev and Lapicki approach (Nikolaev, 1967), (Lapicki et. al., 1980) and extended (modified) for target M-shell. The simultaneous multiple ionisations (SMI) have been considered in the theoretical X-ray production cross-section by modifying the fluorescence yield and Coster-Kronig transition rates by SMI probability for higher shells using Binary-Encounter Approximation. The probability of electron capture becomes a dominating factor if the active target electron binding energy is comparable to the binding energy of the projectile shell where the electron is being captured. However, to obtain the actual capture cross-section contribution in the total ionization phenomena we need to consider the charge state of the projectile inside the target atom. Irrespective of moving with an initial charge state, the projectile acquires a charge state distribution inside the target material and each charge state has a different contribution fraction in cross-section. The distribution has been taken to be the Lorentz distribution about a mean charge state obtained from several empirical models depending on the energy of the projectile. (author)