Effects of autoionization in electron loss from helium-like highly charged ions in collisions with photons and fast atomic particles

摘要

We study theoretically single electron loss from helium-like highly chargedions involving excitation and decay of autoionizing states of the ion. Electronloss is caused by either photo absorption or the interaction with a fast atomicparticle (a bare nucleus, a neutral atom, an electron). The interactions withthe photon field and the fast particles are taken into account in the firstorder of perturbation theory. Two initial states of the ion are considered:$1s^2$ and $(1s2s)_{J=0}$. We analyze in detail how the shape of the emissionpattern depends on the atomic number $Z_{I}$ of the ion discussing, inparticular, the inter-relation between electron loss via photo absorption anddue to the impact of atomic particles in collisions at modest relativistic andextreme relativistic energies. According to our results, in electron loss fromthe $1s^2$ state autoionization may substantially influence the shape of theemission spectra only up to $Z_{I} \approx 35-40$. A much more prominent roleis played by autoionization in electron loss from $(1s2s)_{J=0}$ where it notonly strongly affect the shape of the emission pattern but also maysubstantially increase the total loss cross section.