Many electrón model for multiple ionization in atomic collisions

C. D. ARCHUBI; C. C. MONTANARI; J. E. MIRAGLIA

Freiburg

Congreso; XXV Internacional Conference on Photonic, Electronic and Atomic Collisions; 2007

Internacional Conference on Photonic, Electronic and Atomic Collisions

Multiple ionization is still a complex problem in atomic collisions. Difficulties become more evident in the MeV regime, where Auger-like processes play a relevant role. The aim of this work is to present an  approach based on a many-electron description to deal with complex systems. The collective representation of the electron cloud led to a simple formalism which do not require high computing power, and let us describe Ne or Xe targets with the same degree of complexity. This approach lies upon three theoretical developments:  1.  The transport equation has been solved for an ion traveling through a single atom (inhomogeneous electronic density), leading to the Poisson distribution, instead of the multinomial one.  2. The shellwise local plasma approximation (SLPA) has been improved to obtain the single-ionization probabilities as a function of the impact parameter. The present version employs the Levine and Louie dielectric function, instead of the one by Lindhard, to take into account the energy ionization threshold of each shell. 3. The post-collisional contributions (time delay vacancy production following direct ionization of inner shells) has been included in the Poisson distribution by employing ratios of charge state distribution of the target atoms measured with time-of-flight (TOF) spectroscopy and photoelectron-ion coincidence techniques.      Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data.