Dynamics of transfer ionization in fast ion-atom collisions

Abstract

We consider transfer ionization in collisions of fast (3.6–11 MeV/u) protons, α particles and lithium nuclei with helium atoms. There are just a few basic mechanisms contributing to this process which can be grouped into correlated ones, which crucially depend on the electron-electron interaction, and uncorrelated, which do not need this interaction to proceed. We show that by exploring momentum spectra of the emitted electrons the correlated and uncorrelated mechanisms can be clearly separated from each other. This exploration also enables one to get insight into subtle details of the dynamics of transfer ionization

Transfer Ionization in Collisions with a Fast Highly Charged Ion

“…In the correlated transfer-ionization the velocities of the electrons with respect to the nucleus of the atom in the final state are of the order of v [16]. Besides, in this state the relative velocity of the electrons is also of the same order.…”

“…In the process of correlated transfer-ionization occurring in very fast collisions (v ≫ Z a ) both electrons undergo transitions in which the change in their momenta is much larger than their typical momenta in the initial atomic state. Because of that, even if the projectile would have a low charge, the nucleus of the atom would be merely a spectator during this process [16]. Under such circumstances the so called impulse approximation, in which the role of the atomic nucleus is just to produce the momentum distribution (and binding energy) of the electrons in the initial state, can be used to treat transfer-ionization.…”

“…Let us now say few words about the treatment of the uncorrelated channels of transfer-ionization. Following [8], [14] and [16] we shall present the amplitude for this process as the product of single-electron transition amplitudes for capture and ionization which are obtained using three-body models: continuum-distorted-wave (for capture) and continuum-distorted-wave-eikonal-initial-state (for ionization) [4].…”

“…Indeed, viewing the collision in the rest frame of the projectile we can see that one of the electrons, belonging initially to a bound configuration of moving particles constituting the atom, can make a transition into a bound state of the ion by transferring the energy excess to another atomic electron which, as a result of this, is emitted from the atom in the direction of the atomic motion [8], [14]. In the rest frame of the atom this electron finally moves in the direction opposite to the projectile velocity [8], [14], [16].…”

Time-dependent calculations of transfer ionization by fast proton-helium collision in one-dimensional kinematics

“…In this mechanism, the electron to be transferred rids itself of the excess energy not via the coupling to the radiation field, as in the radiative capture process, but by interaction with the other electron. In their comment on Voitkiv and Ma [13], Popov et al [14] argued that since both the prior and post forms of the first Born amplitude should be identical, the newly discovered electronelectron Auger mechanism was, in fact, contained in the long-known OBK amplitude. In their reply, Voitkiv and Ma [15] retorted this argument by appealing to the physical intuition and analogy between the TI and other related processes.…”