Eur. Phys. J. D (2012) 66: 225
https://doi.org/10.1140/epjd/e2012-30291-1

Regular Article

The dependence of the forward-backward asymmetry parameter on the molecular orientation in angular distributions of emitted electrons in the H₂ ionisation induced by bare ion impact

¹ Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
² Centro Federal de Educação Tecnológica Celso Suckow da Fonseca, 25620-003 Petrópolis, RJ, Brazil
³ Departamento de Física, Universidade Federal de São Carlos, 13565-905 São Carlos, SP, Brazil
⁴ Instituto de Química, Universidade Federal do Rio de Janeiro, 21941-909 Rio de Janeiro, RJ, Brazil

^a e-mail: rodfer@if.ufrj.br

Received: 4 May 2012
Received in final form: 18 June 2012
Published online: 30 August 2012

Abstract

We have studied the angular distributions of electron emission in collisions of bare ions with H₂ oriented target using molecular wave functions calculated with the Schwinger variational iteractive method within the Continuum Distorted Wave-Eikonal Initial State approximation (CDW-EIS-SVIM). By calculating the forward-backward asymmetry parameter for different molecular orientations we show that this parameter depend not only on the perturbation strength, S_p = Z_p / v_p, where Z_p and v_p are respectively the projectile charge and velocity (two-centre effect) and on the outgoing electron velocity, but may also depend on how the molecule is aligned with respect to the projectile incident axis. Doubly differential cross sections (DDCS) for fixed in space molecular target were calculated. The asymmetry parameter was compared with both experimental and theoretical orientation averaged results.