K-shell Ionization Cross Sections Research Articles

α-particle and deuteron impact K-shell ionisation of atoms in binary encounter approximation

K-shell ionisation cross sections for atoms due to the impact of α-particles and deuterons have been calculated in the binary encounter approximation. The effects of Coulomb deflection of the incident projectile and increase in binding of the target electron have been investigated separately. Hartree-Fock velocity distributions for the target electrons have been used in the present work. The calculated cross-sections and the ratio R = σ α /4 σ d have been compared with experimental results and other available calculations. The present calculations are found to give a good account of experimental results.

Cross sections for K-shell ionisation in relativistic heavy-ion collisions

For relativistic heavy-ion collisions K-shell ionisation cross sections are calculated in the semiclassical approximation by using a relativistic description of the electronic states. The calculations are compared with measurements with 4.88 GeV protons and 670 MeV amu-1 Ne ions as projectiles.

K-shell ionization by 16O and 32S ions: Reduced-velocity dependence of the binding effect.

K-shell ionization probabilities ${P}_{K}$ were measured for 2.2-MeV/u $^{16}\mathrm{O}$ ions with impact parameter b=16--51 fm on 24 targets ranging from Sc to Bi. For Bi, the distribution ${P}_{K}$(b) was also measured. Total K-shell ionization cross sections ${\ensuremath{\sigma}}_{K}$ for $^{16}\mathrm{O}$ and $^{32}\mathrm{S}$ projectiles are reported for the same target range. Semiclassical calculations using the velocity-dependent electron binding energies from the relativistic two-center approximation of Andersen, Laegsgaard, and Lund reproduce both ${P}_{K}$ and ${\ensuremath{\sigma}}_{K}$ very well, except where polarization effects become important.

Auger electron spectra in 5.5 MeV/amu Ne q+ and Ar q+ ion impact on Ne

A study of Ne K Auger spectra induced by 5.5 MeV amu Ne 3+ Ne 10+ Ar 6+ and Ar 17+ heavy ions on Ne is presented. Some average quantities (the centroid energy of KLL Auger spectra, the average number of L vacancies produced simultaneously with the K vacancy, the effective charge of the projectile in the actual process, the satellite to total intensity ratio) characterising the KL n ionization process have been extracted from these spectra. Relative K-shell ionization cross sections and KLM to KLL cross section ratios have been evaluated. The deduced experimental Z eff values have been compared with the results of PWBA and BEA calculations. A simple model calculation is made in an attempt to interpret the variation of the probability for the ejection of an L-shell electron ( p L ) as a function of Z eff v p . Some statements regarding individual lines and groups in the Auger spectra are made.

K-Shell ionisation by energetic light ions

Total K-shell ionisation cross sections were investigated for Li ions of 0.2 MeV u ≤ E Lab/M Proj ≤ 2.7 MeV u irradiating very thin single-isotope targets of elements with 24 ≤ Z T ≤ 62. Together with earlier measurements for the ionisation of heavy elements (42 ≤ Z T ≤ 62 by protons and a few measurements for 12C ions bombarding targets with 50 ≤ Z T ≤ 62 the Li data are compared with theoretical calculations for Coulomb ionisation (EC-PSS-R, SCA-BCR); possible origins of systematic discrepancies observed for all projectiles are discussed.

Comment on the relation between the cross section for electron stripping from a helium-like ion in collision with atomic hydrogen and the K-shell ionisation cross section for proton impact

The relationship between the cross section and impact velocity for the electron stripping process and that for the K-shell ionisation process by proton bombardment has been studied. In the case of Li++H to Li2++H( Sigma ), the relationship has been plotted and compared with that for K-shell ionisation of neutral atoms by proton and alpha particle bombardment. The observed similarity indicates that electron stripping occurs in a way similar to inner-shell ionisation by a nucleus and is expressed rather well by the plane-wave Born approximation with some corrections.

Deuteron- and alpha-particle-induced K-shell ionisation of W and Au atoms

Deuteron- and alpha-particle-induced K-shell ionisation cross sections for W and Au were obtained from thick target measurements for low impact velocities. They were compared with proton-induced cross sections in the same range of velocities. Equal velocity cross section ratios are a very stringent test of the corrections incorporated in the PWBA calculations. The sigma d/ sigma p data presented in this paper shed some light on the Coulomb deflection corrections discussed in the literature. The consequences of the inelastic character of the ionisation process are thoroughly examined.

Auger electron spectra in 5.5 MeV amu-qNeq+and Arq+ion impact on Ne

A study of the Ne K Auger spectra induced by 5.5 MeV amu-1 Ne3+, Ne10+, Ar6+ and Ar17+ heavy ions on Ne is presented. Some average quantities (the centroid energy of the KLL Auger spectra, the average number of L vacancies produced simultaneously with the K vacancy, the effective charge of the projectile in the actual process, the satellite to total intensity ratio) characterising the KLn ionisation process have been extracted from these spectra. Relative K-shell ionisation cross sections and KLM and KLL cross section ratios have also been evaluated. The deduced experimental Zeff values have been compared with the results of PWBA and BEA calculations. A simple model calculation is made in an attempt to interpret the variation of the probability for the ejection of an L-shell electron (pL) as a function of Zeff/vp. Some statements regarding individual lines and groups in the Auger spectra are made.

Cross sections for K-shell ionization of Si and Ar by 4 keV to 10 keV electron impact

K-Auger electron emission of Si and Ar produced by 4 keV to 10 keV electrons was measured. Absolute yields were obtained by normalizing to the elastically scattered primary electrons. From the yields cross sections for K-shell ionization were deduced. The cross sections are in good agreement with the results of a fit formula for K-shell excitation in the whole range measured, while they agree with results of PWBA calculations including electron exchange in the Ochkur approximation only for the higher impact energies.

K-Shell Cross Sections Extracted from Measured Charge-State Distributions for F and Si Ions Penetrating C

Charge-state distributions have been measured as a function of foil thickness and incident projectile charge state for 4.5-9.0 v0. F ions and 6.0-9.0 v0 Si ions transmitted through thin carbon foils. The charge-state distributions are analyzed in terms of separate K- and outer-shell populations. The outer-shell population is demonstrated to depend on the number of K vacancies in the ion. The ionic K-shell population inside the solid is described in a three-component model, and cross sections for creation and quenching of single and double K vacancies were extracted from a fit to the data. Based on these cross sections, different types of interactions involving the ionic K shell inside solid carbon could be identified: electron excitation and ionization, electron capture, and spontaneous decay of outer-shell electrons.

K-shell cross sections for analytical electron microscopy

There has during the last few years been a renewed interest in the calculation of ionization cross-sections for use in AEM-based x-ray analysis, due to the fact that modern AEM's can operate up to accelerating potentials of 400 kV. In this regime relativistic effects are considerable and the extrapolation of the “accepted” microprobe-based formulae to these levels is questionable and the relativistic Bethe equation is the most appropriate formulation.

Nonperturbative effects in inner-shell ionization

A theoretical investigation of ion-induced inner-shell ionization is described, in which some physical effects that are nonperturbative in nature are included within the formalism of perturbation theory. In particular, the effects of the dynamical response of the outer electrons under the influence of the incident projectile are considered. Special emphasis is given to the use of nonorthogonal basis states in perturbation theory. Calculations for the proton- and 3He ion-induced total cross sections for K-shell ionization in titanium and copper are performed and compared with experimental data. Significant discrepancies between the theoretical results and the measured values are found to exist. Possible improvements to the theory are discussed.

K-shell ionization due to light ions: The status of cross-sections

In earlier papers, we have shown that the bulk of experimental K-shell ionization cross-sections can be well represented by the Brandt-Lapicki theory. Here we discuss the remaining discrepancies: at low reduced velocity ξ, the Brandt cross-section is too high due to its Coulomb correction. For ξ > 0.6 and nitrogen projectiles, electron capture by the projectile and an increased fluorescence yield enhance the cross-section. Between ξ = 0.25 and ξ = 0.6, a small deficiency of Brandt's binding correction is found, using both experimental data and theoretical results. Krause's fluorescence yields are discussed and various theoretical cross-sections are compared. Light target data are discussed separately, and some chemical effects are pointed out.

K-shell ionisation cross sections for W, Au and U by low-velocity protons

Proton-induced K-shell ionisation cross sections for W, Au and U by low-velocity protons were obtained from thick-target measurements. For the first time the lowest incident energy reached a value less than ten times the binding energy of the K-shell electron (less than nine times in the case of Au). Possible sources of error are thoroughly examined and a comparison with other available experimental results and theoretical values is presented and discussed.

The K-shell ionisation of64Gd,74W and90Th induced by heavy, charged particles

The total K-shell ionisation cross sections were measured relative to nuclear Coulomb excitation cross sections for 64Gd, 74W and 90Th targets bombarded by 4He and 16O projectiles. In the case of 74W, projectiles of 12C and 19F were also applied. The experimental results are compared with the predictions of the SCA-LAL model, and the overall agreement is very good. The data are presented as reduced cross sections and compared with a 'universal' cross section function.

The cross sections for K-shell ionisation of atoms with Z ⩾ 64 induced by low energy protons

For the 165 67Ho and 197 79Au targets, bombarded with 1–3 MeV protons, cross sections for the K-shell ionisation have been determined relative to the known cross sections for the Coulomb excitation of the nuclear collective states. The results are discussed with reference to those from other proton-induced ionisation experiments in targets with Z ⩾ 64, and to the models for the ionisation process.

K-shell ionisation of heavy target elements (42 ⩽ ZT ⩽ 62) bombarded with protons in the energy range 0.5 MeV–6 MeV

Total K-shell ionisation cross sections were measured for the irradiation of thin solid targets ( < 5 μg cm 2 ) of 92Mo, 104Pd, 120Sn, 138Ba, 140Ce, 1142Nd and 144Sm with protons of 0.5 MeV u ⩽ E Lab M Proj ⩽ 6.0 MeV u . Only isotopes were chosen as targets for which internal conversion of de-exciting transitions of nuclear excited states does not contribute to K-shell ionisation. The measured cross sections are compared with theoretical calculations within the framework of the perturbed-stationary state theory and with calculations based on the semiclassical approximation. Only for very low proton energies ( ξ ⩽ 0.25) are there systematic differences between the experimental data and the theoretical calculations; for ξ > 0.25 most of the measured ionisation cross sections agree with both calculations within the experimental errors (9–15%).

Precise X-ray production cross-section measurements of medium Z elements by protons

The K a X-ray production cross sections of 53I, 55Cs, 56Ba and 57La for protons between 1.5 MeV and 3.0 MeV have been measured. Moreover, the K-shell ionization cross sections of 29Cu and 35 Br are reported. The targets are in the form of thin layers mounted on three different types of backings: nuclepore membrane filter, mylar, and thin carbon foil. The experimental results are compared with the most recent formulations of the perturbed stationary state model corrected for Coulomb deflection, relativistic and energy loss effects (ECPSSR), and of the relativistic plane wave Born approximation corrected for binding effect and Coulomb deflection (RPWBA-BC).

Proton impact K-shell ionisation of atoms in binary encounter approximation

K-shell ionisation cross sections have been calculated using Vriens' expressions for ionisation of atoms by proton impact. The effects of Coulomb deflection of the incident proton and increase in binding of the target electron have been investigated separately. Hartree-Fock velocity distributions for the target electrons have been used in the present calculations. The calculated results have been compared with experimental values and other available calculations. The present method is found to give a good account of proton impact K-shell ionisation cross-sections.

Single and Double K-Shell Ionization Cross Sections of Beryllium by C, N, O and Ne Ion Bombardments

Cross sections for single and double K-shell ionization of Be were obtained from K α diagram and hypersatellite X-ray yields produced by C, N, O and Ne ion bombardments with the energies from 0.3 to 1.3 MeV. The data are compared with the theoretical predictions which consider 2pσ-2pπ MO coupling. The results show a good agreement except for the collision system of Ne+Be.