Cross Sections For Single Electron Loss Research Articles

Empirical regularities in the charge-exchange cross sections of ions with nuclear charges from 5 to 10

A method for empirically estimating cross sections for single-electron loss and capture by ions that are heavy ions in gases is proposed. This method is based on similarity laws for the energy dependences of charge-exchange cross sections. The charge-exchange cross sections of ions with nuclear charges ranging from 5 to 10 in gases with energies ranging from 1 keV/nucleon to 100 MeV/nucleon are obtained. These cross sections can be used to estimate the charge-exchange cross sections in solids if a correction for the substance density is taken into account.

Charge-changing processes in collisions of heavy many-electron ions with neutral atoms

Some features of charge-changing processes, namely, electron capture (EC) and electron loss (EL), are considered for heavy many-electron ions colliding with neutral atoms in a wide range of ion energy E = 10 keV/u–100 GeV/u. The discussion is based on cross-section calculations performed by available computer codes, namely, CAPTURE, DEPOSIT and RICODE. The RICODE (Relativistic Ionization CODE), which provides calculation of single-electron loss cross sections in the relativistic energy regime, was recently created on the basis of the relativistic Born approximation and is described in the Appendix A. In addition, a semi-empirical formula for single-electron loss cross sections is suggested based on properties of the Born approximation and numerical calculations by the RICODE program. To cover also the low and intermediate collision energies, EL cross sections are obtained by the recently created DEPOSIT code which provides calculation of single- and multiple-electron as well as the total cross sections. Based on the results obtained by these codes, recommended capture and loss cross sections for heavy ions like xenon, uranium and lead ions colliding with neutral atoms are presented over a wide energy range.

Single electron loss in the collisions of C3+ and atomic hydrogen

This paper studies the projectile electron loss cross sections of C3+ colliding with atomic hydrogen in the frame work of extended over-barrier model at intermediate velocities (25 keV/u–600 keV/u). The electron loss is calculated in terms of the interaction between the screened target nucleus and the active projectile electron and of the interaction between projectile electron and target electron. Compared with the convergent close-coupling calculations, screening and anti-screening calculations, this model satisfactorily reproduces the experimentally obtained energy dependence of the electron-impact ionisation cross sections and the single electron loss cross sections over the energy range investigated here.

Single electron loss in the collisions of lowly charged ions and atomic hydrogen

In this paper, the projectile electron loss cross sections of He +, Li +, Li 2+ and C 2+ colliding with atomic hydrogen are studied in the frame work of the extended over-barrier model at intermediate velocities (25–600 keV/u). The electron loss cross sections are calculated in terms of the interaction between the screened target nucleus and the active projectile electron and of the interaction between the projectile electron and the target electron. Compared with the measurements, this model satisfactorily reproduces the experimentally obtained energy dependence of the single electron loss cross sections over the energy range investigated here.

Electron loss and multiple electron capture ofB2+andC3+ions colliding with Ne and Ar targets

Absolute cross sections for the projectile single-electron loss and single- and double-electron capture of ${\text{B}}^{2+}$ ions colliding with Ne and Ar targets and ${\text{C}}^{3+}$ ions colliding with Ar targets, in the energy range from 0.1 to 4.0 MeV, have been measured. Cross sections for the single capture channel have been calculated using the classical Bohr-Lindhard model, showing good agreement with the experiment. In the single electron-loss process, calculations were performed using both an extended version of the classical-impulse free-collision model and the plane-wave Born approximation (PWBA) for the screening mechanism, added to antiscreening cross sections calculated with the PWBA, thus providing total single electron-loss cross sections. The total cross sections obtained from the former method provided very good descriptions of the single electron-loss measured data, much better than those from the PWBA. The antiscreening calculations have been compared to experimental cross sections for ionization of ${\text{B}}^{2+}$ and ${\text{C}}^{3+}$ ions by electrons, within the independent-particle model, showing a good agreement in the asymptotic high-velocity region.

Asymptotics of the cross section of the electron loss by fast ions in light media

The dependence of the single electron loss cross section on the nuclear charge Z of a projectile and on the nuclear charge Z t of a target atom for fast collisions is studied theoretically using the plane-wave Born approximation and the sum rule. The results of calculations for fast singly and triply charged ions show that the single electron loss cross section increases monotonically as Z and Z t increase. This can be used to interpolate cross sections of processes if there are no experimental data. The results of calculations compare with the experimental and theoretical data of other authors.

Single electron loss by fast ions in helium

The single electron loss cross sections for fast B, N, and Ne ions colliding with He atoms are calculated. In the calculation of the ionization amplitude, the He nucleus screening is taken into account by both the sum rule and the summation over a finite number of excited 1snl (n < 5, l < 2) states and states of the continuous spectrum. The calculated results agree satisfactorily with experimental data.

Experimental and theoretical investigations of single-electron capture andloss inHe+-Ar collisions

Experimental and theoretical investigation of single-electron capture andadditional experimental studies of single-electron loss cross sections inHe+-Ar collisions at impact energies of 1.5-5.0 keV forexperimental studies and from 10 to 4000 keV for the theoreticalcalculations are presented. Comparisons are made with other experimentalresults, for single-electron capture the present measurements confirm thebehaviour observed by previous measurements in the energy range1.5-5.0 keV, except with the data of Eisele and Nagy (1977 J. Chem. Phys. 66 883-5), and for single-electron loss an extrapolation of thehigh-energy results to low energies shows good agreement with the presentdata, giving the general shape of the cross section curve. Our theoreticalcalculations are in good agreement with the experimental data andreproduce the main features of the cross section energy dependence. Wepresent the most important contributions to the total cross sections fromthe partial capture cross section to the He(1s) and He(n = 2) states, withthe former as the dominant channel over the energy region considered.

Experimental study of single-electron loss by Ar+ ions in rare-gas atoms

Absolute differential and total cross sections for single-electron losswere measured for Ar+ ions on rare-gas atoms in the laboratoryenergy range of 1.5 to 5.0 keV. The electron loss cross sections for all thetargets studied are found to be in the order of magnitude between10-19 and 10-22 cm2, and show a monotonically increasingbehaviour as a function of the incident energy. The behaviour of the totalsingle-electron loss cross sections with the atomic target number, Zt,shows different dependences as the collision energy increases. In allcases the present results display experimental evidence of saturationin the single-electron loss cross section as the atomic number of thetarget increases.

N2+formation in collisions betweenN+ions and rare gases

Total cross sections for single-electron loss of ${\mathrm{N}}^{+}$ ions impinging on Ne, Kr, and Xe were measured in the energy range from 1.5 to 5.0 keV. The measured electron-loss cross sections show a monotonically increasing behavior as a function of energy of the incident beam for all the targets studied. Our results are compared with previous experimental data and are found to be in excellent agreement.

Single electron loss of Kr+ ions in gaseous media

Differential and total cross sections for single electron losswere measured for Kr+ ions on gaseous media in the energyrange of 1.0 to 5.0 keV. The single electron loss crosssections for all the targets studied are found to be in theorder of magnitude between 10-22 and 10-20 cm2,and show a rapid monotonically increasing behaviour as afunction of the incident energy; no remarkable differences inthe energy dependence of σ12 were found for any atomstudied. The single electron loss cross sections show a weakerZt dependence in the large Zt region than that given bythe Bohr formula. A striking feature of the results is theexperimental evidence of saturation in the single electron losscross section as the nuclear charge of the target increases.

Production of and in collision of ions with Kr

Absolute differential and total cross sections for single-electron loss and capture were measured from ions on Kr in the energy range of 1.0-5.0 keV. The reduced differential cross sections as a function of are shown to scale reasonably well for both products studied. For single-electron loss, our cross sections are found to be of the order of magnitude of , while for single-electron capture the magnitude is . The measured total cross sections are compared with theoretical models available in the literature.

Single-electron loss and capture for 1.0-5.0 keV colliding with He

Absolute differential and total cross sections for single-electron loss and capture were measured from ions on He in the energy range of 1.0-5.0 keV. The reduced differential cross sections ( versus ) are shown to scale reasonably well for each of the two processes studied. For single-electron loss, our cross sections are found to be of the order of magnitude of . An extrapolation of the high-energy results to low energies shows good agreement with the present data. The total cross section for single-electron capture is compared with other available measurements. These results give a general shape of the whole curve of single-electron capture cross sections for the system over a wide range of energy.

Measurement of charge-changing cross sections in collisions of He and He+ with H2, O2, CH4, CO and CO2

Single- and double-electron loss cross sections of He, and single-electron capture and single-electron loss cross sections of He+ in collisions with H2, O2, CH4, CO and CO2 have been measured in the energy range 0.3-1.8 MeV. From the measured cross sections, charge-changing cross sections in collisions of He and He+ with C have been determined using the Bragg rule. Scaling is examined for electron capture cross sections.

Electron-loss cross-section measurement of 3He ions by the attenuation method

We have measured single-electron loss cross sections of 3He1+ ions for various solid targets such as C, Al, V, Cr, Cu, Ge, Nb, Ag, Sn and Au at 72 MeV by using the attenuation method. In this method residual 3He1+ fractions after charge-changing collisions were measured with a 3He1+ incident beam. Concentrations of contaminating atoms in the target were determined by an independent RBS measurement. It was found that surfaces of almost all the targets were covered with thin oxygen layers by which 3He1+ fractions were reduced by about 10%. Corrections of the observed loss cross sections are made for the surface oxygen layers.

Single electron loss cross sections oF 3He 1+ ions for solid targets at 52, 62 and 72 MeV

Single electron loss cross sections of 3He 1+ ions for solid targets of C, Cu, Ge, Sn and Au were measured at 52, 62 and 72 MeV using the growth method. The free electron collision model for single electron atoms has been extended to all targets and the corresponding calculations have been carried out. The results give fairly good agreement with the experimental values. Results are also compared with other current theories.

Single and Multiple Electron Loss Processes in MeV Heavy Ion-Target Collisions

Experimental data, derived from the study of interactions between MeV heavy ions and gaseous targets, are presented which illustrate important physical aspects such as the dependence of cross sections on projectile velocity, and projectile and target atomic numbers. Included are data which reflect the importance of the electron binding energy, the existence of shell effects, the possibility of target polarizability, and the presence of non-additivity and density effects in electron loss processes. Charge state yield versus scattering angle, a prescription for relating total single electron loss cross section per atom atomic and molecular target data and formulas which predict electron loss cross sections with reasonable accuracy are also given.

Charge-Changing Collisions of 0.7–2.0 Mev Helium Beams in Various Gases. II. Electron Loss

The single and double electron loss cross sections σ 01 , σ 12 and σ 02 of helium beams have been measured for target gases H 2 , He, N 2 , O 2 , CO 2 , CH 4 , C 2 H 6 and C 3 H 8 in the energy range from 0.7 to 2.0 MeV. By using cross sections for carbon-containing molecules, the additive rule was verified for the electron loss processes of helium beams in this energy region. Loss cross sections for a carbon atom were deduced. Empirical formulae for single electron loss cross sections were obtained for atomic targets H, He, C, N and O. The ratio between two single electron loss cross sections, σ 01 /σ 12 , and the ratio between single and double electron loss cross sections, σ 01 /σ 02 are discussed.

Total Born-approximation cross sections for single-electron loss by atoms and ions colliding with atoms

The first Born approximation (FBA) is applied to the calculation of single-electron-loss cross sections for various ions and atoms containing from one to seven electrons. Screened hydrogenic wave functions are used for the states of the electron ejected from the projectile, and Hartree-Fock elastic and incoherent scattering factors are used to describe the target. The effect of the target atom on the scaling of projectile ionization cross sections with repect to the projectile nuclear charge is explored in the case of hydrogenlike ions. Also examined is the scaling of the cross section with respect to the target nuclear charge for electron loss by ${\mathrm{Fe}}^{+25}$ in collision with neutral atoms ranging from H to Fe. These results are compared to those of the binary-encounter approximation (BEA) and to the FBA for the case of ionization by completely stripped target ions. Electron-loss cross sections are also calculated for the ions ${\mathrm{O}}^{+i}(i=3\ensuremath{-}7)$ and ${\mathrm{N}}^{+i}(i=0\ensuremath{-}6)$ in collision with He targets in the energy range of \ensuremath{\sim}0.1 to 100 MeV/nucleon. These results are found to be in excellent agreement with the available data near the peak of the ionization cross section.

Collisional detachment cross sections for H-and He-at high energies

The single- and double-electron-loss cross section for H- and He- ions passing through H2, He, N2, Ne and Ar gas targets have been studied in the energy range 50-500 keV for H- impact and 100 keV-3 MeV for He- impact. H- and He- ions were formed from H+ and He+ by charge transfer in a gas cell and the cross sections were determined by the initial-growth method. The experimental cross sections for single-electron loss are compared with theoretical estimates, based upon the semi-empirical impulse approximation of Bates and Walker (1967). A comparison of the experimental results for H- and those for He- impact at equal impact velocities indicates an error of up to 50% in the basic, non-empirical part of the Bates-Walker theory.