Contribution Of Electron Capture Research Articles

K-shell ionization cross sections of Cu, Zn and Ge by 3–5 MeV/u Si-ion bombardment

The K x-ray spectra of different targets (Cu, Zn, and Ge) induced by 3 to 5 MeV/u Si projectile ions have been measured to determine the K-shell ionization cross-section. A significant difference is observed between the measurements and theoretical estimates, where the theoretical ones are about 28–35% of the experimental results. Such difference is reduced to a good extent 51%–56% if multiple ionization effects are taken into account. Remaining discrepancy may be attributed to the electron capture contribution.

Introducing electron capture into the unitary-convolution-approximation energy-loss theory at low velocities

Recent developments in the theoretical treatment of electronic energy losses of bare and screened ions in gases are presented. Specifically, the unitary-convolution-approximation (UCA) stopping-power model has proven its strengths for the determination of nonequilibrium effects for light as well as heavy projectiles at intermediate to high projectile velocities. The focus of this contribution will be on the UCA and its extension to specific projectile energies far below 100 keV/u, by considering electron-capture contributions at charge-equilibrium conditions.

K X-ray production by 3–4 MeV proton impact on selected lanthanoids

Measurements of K-shell X-ray production cross sections induced by proton beams with energies between 3 MeV and 4 MeV are presented. The studied elements were Ce, Nd, Gd, Dy, and Ho, as thick targets. The measured cross sections are evaluated through comparisons with the ECPSSR model, the eECPSShsR-UA theory, the adiabatic perturbation (also known as direct molecular orbital, or MO) theory, and the empirical fits of Kahoul et al. using a scaling based on the reduced velocity parameter ξ K R in every case. Consideration is given to multiple ionization effects and electron capture contribution to K-shell ionization. It is shown that the experimental results are in good agreement with the theoretical predictions in the whole measured ξ K R range.

K X-ray emission induced by 12C 4+ and 16O 5+ ion impact on selected lanthanoids

Measurements of K-shell X-ray production cross sections by 12C 4+ (beam energies between 12 MeV and 14 MeV), and 16O 5+ ions (with energies between 12.5 MeV and 15 MeV) are presented. The target elements were selected lanthanoids (Ce, Gd, Dy, Ho and Er). The resulting measurements are evaluated through comparisons with the eECPSShsR-UA theory, the MECPSSR model and the adiabatic perturbation (also known as direct molecular orbital, MO) theory, using a scaling based on the reduced velocity parameter ξ K R . Consideration is given to multiple ionization effects and electron capture contribution to K-shell ionization. An evaluation with previously published values is also given. It is shown that the behavior of the ratios of experimental to theoretical cross sections is different for both ions. The models do not seem to be accurate to predict the X-ray production cross sections for 12C 4+ ions, while the MECPSSR theory predicts much better the experimental data for 16O 5+ than the eECPSShsR-UA.

Gamow-Teller beta decay of 105Sn

The β-decay of 105Sn was re-investigated at the ISOL facility of GSI Darmstadt by using a total absorption spectrometer. The experimental results include the half-life and β-delayed proton branching ratio of 32.7(5)s and 1.1(4) . 10-4, respectively, and the contribution of electron capture to the 105Sn decay of 0.420(35). The Gamow-Teller strength distribution peaking at 3.6MeV was measured, yielding a summed Gamow-Teller strength of 3.0(4). The latter data are discussed in comparison with shell-model predictions based on an empirical interaction.

K X-ray production by 12C 4+ ion impact on selected elements

Measurements of K-shell X-ray production cross sections by 12C 4+ ions with energies between 6 and 9 MeV are presented. The target elements were Ti, Mn, Fe, Cu, Ga, Ge, Pd, Ag, and In. The measured cross sections are evaluated through comparisons with the ECPSSR model, the ECPSSR-UA theory, the MECPSSR model and the adiabatic perturbation (also known as direct molecular orbital) theory, using a scaling based on the reduced velocity parameter ξ K R . Consideration is given to multiple ionization effects and electron capture contribution to K-shell ionization. It is shown that the models are not suitable for predicting accurately the X-ray production cross sections in the whole measured ξ K R range.

L-shell ionization of Cd, Sb, Te, Ba, La, Eu, Tb and Yb by 16O ions in the energy range from 0.19 to 0.75 MeV u−1

Lα1,2, Lβ1,3,4, Lβ2,15, Lγ1(5) and Lγ2,3(4,4′) X-ray production cross-sections have been measured on selected medium-Z elements using 16O ions with energies from 0.19 to 0.75 MeV u−1. Calculated L-subshell ionization cross-sections were compared with the predictions of the direct ionization theories: the ECPSSR theory, the semiclassical approximation (SCA) in the united atom limit (SCA-UA) and SCA coupled-channel calculations (SCA-CC) involving a few lowest lying states. For the ECPSSR theory, large discrepancies were found for all three subshells. Better overall agreement between the experiment and theory was found for the SCA-UA theory. SCA-CC calculations improved the agreement between experiment and theory for the L2-subshell in the very adiabatic region. By measuring the Lα X-ray production cross-sections on W targets of different thickness, possible contribution of electron capture (EC) to the X-ray production cross-section was estimated to be less than 20%. The degree of multiple ionization of outer shells caused by heavy ion bombardment was estimated from the X-ray line energy shifts and by comparing the X-ray intensity ratios for heavy ions and protons.

Electron-capture contribution to the stopping power of low-energy hydrogen beams passing through helium.

The energy loss of hydrogen beams traversing a helium gas target is calculated using the charge-state approach. The first Born approximation is used for the neutral charge-state and the continuum-distorted-wave--eikonal-initial-state model for the proton charge state. This model takes into account distortion effects due to the long-range Coulomb potential. From the cross sections for the different reaction channels we obtain the equilibrium charge-state fractions, the electronic stopping power associated with each reaction channel, and the mean electronic stopping power. This information allows a detailed study of the velocity dependence at low impact velocities.

X-ray production in fluorine by highly charged boron, carbon, and oxygen ions

K-shell X-ray production cross sections of fluorine have been measured as a function of ion charge state for boron and carbon ions at 10 MeV and oxygen ions at energies of 8, 10, and 12 MeV. From the projectile charge-state dependence of the cross sections, both direct-ionization and electron-capture contributions were extracted for comparison to the Coulomb ionization theory, ECPSSR, which accounts for energy loss and Coulomb deflection of the projectile as well as for relativistic and perturbed stationary states of the inner-shell electrons.

The evolution of ΔE/ΔX for 7 MeV/u 16O ions in carbon

The energy loss of 7 MeV/u 16O ions passing through solid carbon targets was measured. The targets were sufficiently thin to determine ΔE/ΔX of O 8+ and O 7+ ions separately. The evolution of ΔE/ΔX and charge state fractions with foil thickness provided data from which estimates of the energy loss contribution of electron capture and loss were obtained. This contribution is significant and greater than simple estimates.

Energy loss and straggling accompanied by charge exchange

Energy loss and straggling of heavy ions have been studied. The conventional target excitation contributions are estimated on the basis of the dielectric function method together with the local electron density model. In addition, electron capture contributions are estimated in a classical atomic picture, which are expressed by simple analytical forms. The average charge of traversing ions is determined by an empirical formula. Electron capture contributions becomes large and comparable at relatively low velocities, where they are proportional to the average charge of ions. At high velocities, on the other hand, these contributions are negligible. Charge exchange processes are found to contribute to the slowing-down as corrections.

K-shell ionization induced by 30 MeV/u argon and neon beams

We have studiedK-shell ionization induced by 30 MeV/u Ne and Ar projectiles on target atoms with atomic numbers ranging from 27 to 90. X-ray production cross sections and energy shifts were measured with Si(Li) detectors. In most cases satisfactory agreement between measurements and theoretical direct ionization cross sections is obtained when the contribution of electron capture is included. The influence of multiple ionization on the fluorescence yield ωK is discussed.

M-shell x-ray-production cross sections in thin targets ofAu79,Pb82,Bi83, andU92by 0.3—2.6-MeVH+11andHe+24ions

$M$-shell x-ray-production cross sections are reported for $_{1}^{1}\mathrm{H}^{+}$ and $_{2}^{4}\mathrm{He}^{+}$ ions incident on thin targets of $_{79}\mathrm{Au}$, $_{82}\mathrm{Pb}$, $_{83}\mathrm{Bi}$, and $_{92}\mathrm{U}$. The energy of the ions ranged from 0.3 to 2.6 MeV in increments of 0.1 MeV. The first Born calculations overpredict the data at all energies studied. The perturbed-stationary-state calculations with energy loss, Coulomb deflection, and relativistic effects agree with the present data for both $_{1}^{1}\mathrm{H}^{+}$ and $_{2}^{4}\mathrm{He}^{+}$ ions at \ensuremath{\sim}0.35 MeV/u, overpredict the data at higher $\frac{{E}_{1}}{{A}_{1}}$, and underpredict the data at lower $\frac{{E}_{1}}{{A}_{1}}$. The electron-capture contribution to the target ionization is calculated to be less than 3.4% for the targets, projectiles, and energies reported in this work.

Projectile Charge State Dependence of M-Shell Ionization of Au, Pb, Bi and U by 1.42-MeV/amu Fluorine Ions

The present study was undertaken to determine the direct ionization and electron capture contributions to vacancy production in the M-shells of 79Au, 82Pb, 83Bi and 92U for incident 199F ions. M-shell x-ray production cross sections have been measured for 1.42-MeV/amu 199Fq+ ions for q=4,5,6,8,9. Enhancements in the target x-ray production cross sections were observed for projectiles with one and two K-shell vacancies over those without K-shell vacancies. Direct ionization and electron capture contributions to the vacancy production were extracted from the data and compared to the plane wave Born approximation and to the Oppenheimer-Brinkman-Kramers calculations of Nikolaev, respectively.

Projectile-charge-state dependence of targetL-shell ionization by 1.86-MeV/amu fluorine and silicon ions and 1.8-MeV/amu chlorine ions

$L\ensuremath{\alpha}$ x-ray-production cross sections have been measured for solid targets of $_{60}\mathrm{Nd}$, $_{67}\mathrm{Ho}$, and $_{79}\mathrm{Au}$ for 1.86-MeV/amu $_{9}^{19}\mathrm{F}$ and $_{14}^{28}\mathrm{Si}$, and 1.8-MeV/amu $_{17}^{35}\mathrm{Cl}$ ions as a function of the incident charge state. From the projectile-charge-state dependence of the cross sections, both direct-ionization and electron-capture contributions were extracted for a comparison to Coulomb ionization theories. The data provide supporting evidence for the theory of electron capture with a reduced binding effect. With standard fluorescence and Coster-Kronig yields uncorrected for multiple-ionization effects, the direct ionization theories did not simultaneously reproduce the projectile-${Z}_{1}$ and target-${Z}_{2}$ dependences of the data.

Projectile charge state dependence of target Lα x-ray production

Lα x-ray production cross sections have been measured for thin solid targets of 60Nd, 67Ho, and 79Au (pt<12 μg/cm2) for 1.86 MeV/amu 199F and 2814Si, and 1.8 MeV/amu 3517Cl ions as a function of the incident charge state. From the projectile charge state dependence of the cross sections, both direct ionization and electron capture contributions were extracted for a comparison to Coulomb ionization theories. The data provide supporting evidence for the theory of electron capture with a reduced binding effect.

Electron capture from inner shells by fully stripped ions

Cross sections for electron capture from inner atomic shells by fully stripped ions, of velocities high compared to the electron velocities in the inner-shell orbits, are calculated in the second Born approximation. The theory of Drisko for electron capture by protons from hydrogen is generalized to projectiles and targets of arbitrary atomic numbers ${Z}_{1}$ and ${Z}_{2}$, respectively. For ions of low velocity, the effects of binding and Coulomb deflection are accounted for in a manner similar to that of Brandt and his co-workers in the theory for direct ionization to the continuum of the target atom. The results are in good agreement with experimental capture cross sections, whereas the Oppenheimer-Brinkman-Kramers approximation overestimates such cross sections. The contribution of electron capture to inner-shell ionization cross sections increases with increasing $\frac{{Z}_{1}}{{Z}_{2}}$ and brings them into agreement with experiment.

K-shell ionization of elements Ca to Zn for 0.5 to 2.5-MeV/amuN14-ion bombardment

Target $K$-shell x-ray production cross sections, x-ray energy shifts, and $\frac{K\ensuremath{\beta}}{K\ensuremath{\alpha}}$ ratios have been measured for 7-35-MeV $^{14}\mathrm{N}$ ions on thin solid films of Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn. Comparisons of the data were made with theoretical predictions obtained from the binary-encounter approximation and the plane-wave born approximation (PWBA). These theories were found to overpredict the experimental data by a factor of 10 at the lower energies. However, at the lower energies, the PWBA, with modifications for increased target electron binding, Coulomb deflection, target electron polarization, and relativistic effects produced results in good agreement with the experimental data. At higher energies, a systematic deviation of the theoretical predictions from the experimental data was found which increases as the ratio of $\frac{{Z}_{1}}{{Z}_{2}}$ becomes larger. Corrections to the fluorescence yields attributable to multiple ionization processes and the addition of electron capture contributions to the previously indicated direct ionization theories produced results in excellent agreement with the experimental data with the exception of those for the light elements at the highest energies.

Capture of ArgonK-Shell Electrons by 2.5- to 12-MeV Protons

Using coincidence techniques, we have measured the cross section for capture of electrons from the $K$ shell of argon atoms by protons in the energy range from 2.5 to 12 MeV. Of the total cross section for electron capture, the contribution of capture from the argon $K$ shell increases with proton energy from 0.5% at 2.5 MeV to 47% at 12 MeV. The contribution of electron capture to the total argon $K$-shell tonization cross section decreases from 0.4% at 2.5 MeV to less than 0.1% at 12 MeV.