Eur. Phys. J. D (2014) 68: 354
https://doi.org/10.1140/epjd/e2014-50442-6

Regular Article

Laser-assisted ionization-excitation of helium by electron impact at large momentum transfer

¹ Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Moscow Region, 141980 Dubna, Russia
² Department of Nuclear Physics and Quantum Theory of Collisions, Faculty of Physics, Lomonosov Moscow State University, 119991 Moscow, Russia

^a e-mail: bulychev@theor.jinr.ru

Received: 10 June 2014
Received in final form: 26 August 2014
Published online: 25 November 2014

Abstract

Ionization of a helium atom by electron impact in the presence of laser radiation is studied theoretically. The kinematic regime of high impact energy and large momentum transfer is considered. The S-matrix of the process is treated within the first Born and binary-encounter approximations. Triple differential cross sections are calculated for the cases when the residual He⁺ ion is left both in the ground (n = 1) and in the first excited (n = 2) states in the presence of a laser field with frequency ω = 1.55 eV and intensity I = 5 × 10¹¹ W/cm². The laser-assisted cross sections corresponding to n = 2 are found to be more sensitive to the electron-electron correlations in helium than the field-free ones.