Regular Article

Energy and angular distribution of electrons ejected from water by the impact of fast O⁸⁺ ion beams

¹ Tata Institute of Fundamental Research, Homi Bhabha Road, Coloba, Mumbai 400005, India
² Institute de Fisica Rosario (CONICET-UNR), Universidad Nacional de Rosario, 2000 Rosario, Argentina

^a e-mail: lokesh@tifr.res.in

Received: 19 April 2017
Received in final form: 26 August 2017
Published online: 18 January 2018

Abstract

Double differential cross sections (DDCS) of electrons emitted from vapor water molecules (in vapor phase) by 2.0 MeV/u and 3.75 MeV/u bare oxygen ion impact have been measured by continuum electron spectroscopy technique. The ejected electrons were detected by an electrostatic hemispherical deflection analyzer over an energy range of 1–600 eV and emission angles from 20^∘ to 160^∘. The DDCS data has been compared with the continuum-distorted-wave-eikonal-initial state (CDW-EIS) approximation and a reasonable agreement was found with both version of the models i.e. post and prior version. By numerical integration of the DDCS data, the single differential cross section (SDCS) and total ionization cross section (TCS) were obtained. The obtained TCS results were compared with other available TCS results for water target within the same energy range. The total ionization cross sections values are seen to saturate as the projectile charge state (q_p) increases, which is in contrast to the first-Born predicted q_p² dependence. This is also in contrast to the prediction of the CDW-EIS models.