Ionization Cross Sections For Proton Impact Research Articles

Proton-impact ionization cross sections of adenine measured at 0.5 and 2.0 MeV by electron spectroscopy

Double-differential ionization cross sections (DDCSs) of vapor-phase adenine molecules (${\mathrm{C}}_{5}{\mathrm{H}}_{5}{\mathrm{N}}_{5}$) by 0.5- and 2.0-MeV proton impact have been measured by the electron spectroscopy method. Electrons ejected from adenine were analyzed by a 45${}^{\ensuremath{\circ}}$ parallel-plate electrostatic spectrometer over an energy range of 1.0--1000 eV at emission angles from 15${}^{\ensuremath{\circ}}$ to 165${}^{\ensuremath{\circ}}$. Single-differential cross sections (SDCSs) and total ionization cross sections (TICSs) were also deduced. It was found from the Platzman plot, defined as SDCSs divided by the classical Rutherford knock-on cross sections per target electron, that the SDCSs at higher electron energies are proportional to the total number of valence electrons (50) of adenine, while those at low-energy electrons are highly enhanced due to dipole and higher-order interactions. The present results of TICS are in fairly good agreement with recent classical trajectory Monte Carlo calculations, and moreover, a simple analytical formula gives nearly equivalent cross sections in magnitude at the incident proton energies investigated.

Charge-equilibration of Fe ions accelerated in a hot plasma

We examine the energy-dependent rates of charge-changing processes of energetic Fe ions in the hot plasma of the solar corona. For ionization of the Fe-ion projectile in collisions with ambient protons, three different methods of estimating the corresponding ionization cross sections are presented and compared. Proton-impact ionization is found to be significant irrespective of the particular method used. Differences in the proton-impact ionization cross sections' estimates are shown to have little effect in calculating highly nonequilibrium Fe charge states during acceleration, whereas equilibrium charge states are sensitive to such differences. A parametric study of the Fe charge-equilibration comprises (i) impact of the ambient plasma density, and (ii) the energy dependence impact of the acceleration rate upon the charge-energy profiles and upon the estimated values of the density acceleration-time product. We emphasize potential importance of careful measurements of charge-energy profiles along with ion energy spectra for determining the energy dependence of ion acceleration time and the energy dependence of the leaky-box escape time.

Relativistic electron- and proton-impact ionization of highly stripped heavy ions determined from projectile-electron loss inH2and He

We show that electron- and proton-impact ionization cross sections for highly stripped heavy ions can be deduced from the projectile-electron-loss cross sections determined by collisions with a ${\mathrm{H}}_{2}$ and a He target. We measure electron loss for 100- and 380-MeV/u ${\mathrm{Au}}^{52+}$, and 405-MeV/u ${\mathrm{U}}^{86+}$ in ${\mathrm{H}}_{2}$ and He targets, and extract the electron- and proton-impact ionization cross sections. Our results are compared with calculations and with channeling experiments.

Thermal ionization effects on inner-shell line emission for Au target heated by intense light ion beams

In order to deduce the experimental beam conditions from the observed x-ray line emission spectrum of high Z elements, atomic radiative data for transition energies and oscillator strengths, ion-atom impact ionization cross sections, Coster–Kronig yields, and fluorescence yield are needed. In this paper, we report on calculations to study the dependence of these atomic data on ionization stage. It has been found that proton impact ionization cross sections decrease slowly with increasing ionization stage, and the fluoresence yields have discrete jumps when the dominant Auger, Coster–Kronig transitions become energetically forbidden. Our study indicates that thermal ionization effects are not important for the dominant K-, L-, and M-line emissions for plasmas with Te ∼ 102 eV.

Numerical simulation of emission spectra from ion beam-heated aluminum plasmas

Non-local thermodynamic equilibrium radiative transfer calculations have been performed to predict emission spectra from plasma heated by intense proton beams. Multilevel, steady-state atomic rate equations were solved self-consistently with the radiation field to determine excitation and ionization populations. Ion beam effects were, included in the rate equations. Proton-impact ionization cross sections were calculated using a plane wave Born approximation model with Hartree-Fock wave functions for the electrons. We examined the dependence of emission spectra on the temperature and thickness of the plasma. In addition, Kα satellite line spectra were computed to assess its potential as a temperature diagnostic. Calculated Kα spectral results are compared with recent Particle Beam Fusion Accelerator II experimental data.

Electron production in proton collisions: total cross sections

Existing data on the ionization of neutral atoms and molecules by proton impact are reviewed, and electron production cross-section data are collected. The three major experimental methods are discussed and possible sources of error identified. Some theoretical cross sections are discussed, and well-established methods of relating them to measured cross sections are reviewed. A mathematical equation is fitted to the weighted experimental data for each target, and these fits are adjusted to be consistent with appropriate theoretical calculations and with electron impact and photoionization data. Recommended values of total cross sections for proton-impact ionization are given.

Doubly differential cross sections for proton-impact ionization of argon

Proton-impact-ionization cross sections for argon which are differential in the energy and angle of the ejected electron have been calculated within the framework of the Born approximation using both Hartree-Slater and Hartree-Fock wave functions for the ejected electron. Results of the two types of calculations are compared with each other and with experiment. Differential cross sections for all five sub shells of argon are examined and particular attention is given to some interesting features of the $K$-shell cross sections. The range of applicability of the theoretical models is discussed.

Ionization, dissociation, and heating efficiencies of cosmic rays in a gas of molecular hydrogen

view Abstract Citations (105) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ionization, dissociation, and heating efficiencies of cosmic rays in a gas of molecular hydrogen. Cravens, T. E. ; Dalgarno, A. Abstract Calculations are presented for the efficiencies with which cosmic rays (having energies of 1-100 MeV) traversing a molecular hydrogen gas produce H2(+), H(+), and H(-) ions, and H atoms. More specifically, detailed descriptions are made of both the primary and secondary processes of such rays, noting parameters including proton impact ionization cross sections and mean energies of secondary electrons. Publication: The Astrophysical Journal Pub Date: January 1978 DOI: 10.1086/155833 Bibcode: 1978ApJ...219..750C Keywords: Cosmic Rays; Gas Dissociation; Gas Heating; Gas Ionization; Hydrogen Clouds; Interstellar Gas; Energy Conversion Efficiency; Gas-Ion Interactions; Hydrogen Atoms; Hydrogen Ions; Space Radiation; Cosmic Rays:Dissociation; Cosmic Rays:Heating; Cosmic Rays:Ionization full text sources ADS |

Ionization of sodium and potassium vapour by 20-100 keV H+and He+ions

A modulated crossed-beam technique has been used to study the ionization of potassium and sodium vapour by 20-100 keV H+ and He+ ions. Absolute cross sections sigma e for electron production have been determined from the gross yield of electrons. Mass spectrometric measurements of the relative abundance of secondary ion species, together with measurements (in a subsidiary experiment) of the total one-electron capture cross section sigma 10 have been used to determine cross sections for Na+, K+, and K2+ formation. Proton impact ionization cross sections are shown to be in generally poor accord with theoretical estimates based on both the classical impulse and Born approximations.

Classical impulse approximations

The classical impulse approximation to the electron and proton impact ionization cross sections is expressed as u2Q(y) = g(y) m2, where g(y) m2 is a unique function of y = E1/u (E1 being the impact energy and u the ionization potential) for a given incident particle of mass m2. Results are presented for H and Li, and are compared with the Thomson and the Born approximations.