Ionization of atoms and molecules using 200-keV protons and 5.5-MeV/u bare C ions: Energy-dependent collision dynamics

Abstract

Using electron spectroscopy technique, we measure the absolute double-differential cross sections (DDCSs) of electrons emitted in collisions of 200-keV protons on He, CH 4 , and O 2 and 5.5-MeV/u bare C ions colliding on O 2 . The emitted electrons are measured in the energy range from 1 to 400 eV for He and CH 4 targets and up to 600 eV for O 2 to include the K-LL Auger line of oxygen. The electrons are detected over different emission angles varying from 20 • in the extreme forward direction to 160 • in the backward direction. The single-differential cross section (SDCS) and total cross section are deduced from the measured DDCSs spectra for all the targets. The DDCS and SDCS are compared with the state-of-the-art continuum distorted wave-eikonal initial state (CDW-EIS) theoretical model. The CDW-EIS model provides excellent agreement with the oxygen data at MeV energy, whereas the deviation in the case of keV energy is substantial, in spite of having nearly the same perturbation strength. The forward-backward angular asymmetry shows a saturation effect in the case of keV energy protons but no such signature is observed for the high-energy collision. A systematic analysis reveals that the asymmetry at low electron energy is sensitive to the associated atomic or molecular structure and is in close agreement with the theory.

Dynamic effective charge in the continuum of the CDW-EIS model for ionization in ion–atom collisions: angular and energy dependence

“…In figure 3, are presented the single ionization DDCS as a function of the angular distributions for He impacted by 200 keV proton. For the case of forward emission, all theoretical models give similar results and an overestimation of the experimental DDCS taken from [22] can be seen for emission energies larger than 25 eV. Nevertheless, it can also be seen that an excellent agreement is obtained when compared to the data taken from [23].…”

“…In figure 4, the angular distributions of the DDCS, at different electron energies, for ionization of Ne by 5 MeV u −1 [9], dash-dot green line CDW-EIS with numerical functions, dash-dot-dot magenta line present DC-CDW-EIS for H 0 impact. Experiment data: circles [22] and triangles [23].…”

“…Theory: solid red line presents DC-CDW-EIS, dashed black line CDW-EIS, dotted blue line DC-CDW-EIS from[9], dash-dot green line CDW-EIS with numerical functions, dash-dot-dot magenta line present DC-CDW-EIS for H 0 impact. Experiment data: circles[22] and triangles[23].…”

Collision site effect on the radiation dynamics of cytosine induced by proton

“…In order to improve understanding and prediction ability of harmful properties of the ionizing radiation, many efforts have been devoted to investigating the elementary reactive processes occurring during the initial radiation attack and afterwards at the molecular level. [9][10][11][12][13][14][15][16] These studies have shed light on the understanding of the ionizing radiation of biomolecules impacted by energetic ions. In contrast to the studies of high-energy proton-induced process, investigation concerning low-energetic proton interactions with DNA and its constituents are rather scarce, and a number of details have not yet been investigated.…”