L-subshell Ionisation Cross Sections Research Articles

L-subshell ionisation studies of Ta, W and Pt with protons

L-subshell ionisation cross-sections for Ta, W and Pt by proton impact in the energy range of 2–5.2 MeV have been determined from the experimental data on X-ray production cross-section and the currently available radiative transition probabilities, fluorescence and Coster–Kronig factors of Krause, Werner and Jitschin and Xu. The measured ionisation cross-sections and their ratios are compared with the results of ECPSSR and RPWBA-BC theoretical calculations and previously reported experimental results. The deviations in the various L subshell ionisation cross-sections with three sets of decay yield parameters are found to be less than 20%. Our results of absolute L-subshell ionisation cross-sections and their ratios are in better agreement with the theoretical calculations as compared to previously reported experimental results. The L-subshell coupling effects are found to be weak for the elements of Ta, W and Pt in the energy region 2–5.2 MeV by proton impact.

L-subshell ionisation cross sections by proton bombardment

Experimental L-subshell ionisation cross sections are discussed. Maps of measured cross sections in atomic number and velocity parameter coordinates are presented. A dependence of ionisation cross sections on atomic number is also discussed.

Investigation of Coulomb deflection effects on L3-subshell alignment and L-subshell ionisation cross sections

The alignment of the L3 subshell has been determined from the measured angular distribution of the Ll X-ray line of gold ionised by 0.3 MeV protons and 0.4-0.66 MeV deuterons. For deuteron impact the absolute value of the alignment parameter has been found to be larger than earlier results for proton and helium projectiles of the same velocities, indicating the presence of a projectile atomic number dependence of L3-subshell alignment at these low projectile velocities. The ratios of L-subshell ionisation cross sections for Sm, Er and Au by 0.2 MeV u-1 proton and deuteron impact and those for Au by 0.3 MeV u-1 proton and deuteron impact are also reported. The Coulomb deflection factor deduced from these data has been compared with different types of Coulomb deflection factors, and it is found to be in good agreement with the Coulomb deflection factor of Anholt et al (1979) and that of Brandt and Lapicki (1979).

Dy and Yb L-subshell ionisation by proton impact

L-subshell ionisation cross sections were determined experimentally for Dy and Yb bombarded by 1-3 MeV protons. Thin carbon-backed targets were employed and the L X-rays emitted were measured with Si(Li) X-ray detector, the efficiency of which was measured independently. Target thicknesses were determined using the Rutherford back-scattering technique. The measured cross sections and their ratios were compared with the predictions of the PWBA and the CEPSSR theories, with particular attention being paid to the energy dependence exhibited by the cross sections. Factors which may account for the significant discrepancies observed between experiment and theory are noted.

L-subshell ionisation for 4He ion bombardment of tellurium

L-subshell ionisation cross sections for 4He ion bombardment of Te in the energy range 0.6−5.0 MeV, obtained by means of X-ray production measurements, have been compared with the predictions of different theories (binary encounter approximation, plane-wave Born approximation, semiclassical approximation). The effects of various corrections taking into account binding modifications, polarisation and relativistic motion of the atomic electrons and Coulomb retardation and energy loss of the projectile have been considered. The binding modification turns out to be the most relevant correction, but it is still inadequate to describe the low energy part of the cross sections.

L-shell ionisation of some heavy elements by proton and helium ion impact

The L-X-ray production cross sections for L α1, 2, L γ 1, 5 and L γ2, 3, 6 transitions have been measured for thin targets of nine heavy elements (Ag, Sn, Sb, Te, Ho, Ta, W, Pt and Bi) by proton and helium ion impact in the energy range 1.5 to 3.8 MeV. The ionisation cross sections for the L 1, L 2 and L 3 subshells were extracted using fluorescence and Coster- Kronig yields of Krause and emission rates of Scofield. The influence of the uncertainties of these atomic parameters on the resulting cross sections was taken into account and discussed. The measured L-subshell ionisation cross sections were compared with results reported by other authors and with predictions of the ECPSSR theory of Brandt and Lapicki. Possible explanations for the observed discrepancies for the L 1−, L 2− and L-subshells are discussed.

L-shell ionisation of medium and heavy elements by 1-3 MeV incident protons

Measurements have been made of the L X-ray emission from thin targets of Dy, Yb, W, Au, Pb, Bi, Ti and U bombarded by protons of energy 1-3 MeV. From these measurements the L-subshell ionisation cross sections have been determined and compared with the predictions of the CEPSSR theory. The ratios of the experimental to theoretical cross sections are presented as a function of the corrected, reduced proton velocity parameter, xi LiR. Significant discrepancies occur for the L1 and L2 subshells for xi LiR<0.7, and the L2-subshell cross sections are underpredicted by the theory for all elements studied. Possible reasons for the observed discrepancies are discussed. The atomic number dependence of the experimental L subshell and total cross sections is presented for 2 MeV incident protons.

Proton-induced L-subshell ionisation on Cd, Sb and Te

L X-ray production cross sections for protons impinging on thin targets of Cd, Sb and Te have been measured in the energy range 0.3-2.0 MeV. L-subshell ionisation cross sections have been extracted and compared with existing data and with the predictions of the perturbed stationary-state theory including corrections for energy loss, Coulomb deflection and relativistic effects (ECPSSR), the binary encounter approximation taking into account the binding effect and Coulomb retardation (BEABC) and the semiclassical approximation with binding, energy loss, Coulomb deflection and relativistic corrections included (SCABCR). Generally, good agreement has been found, slightly favouring the ECPSSR theory over the others. A better insight can be achieved by looking at the ratios of the subshell ionisation cross sections, owing to the nodal structure of the 2s1/2 wavefunction. These results are in good agreement with analogous measurements on neighbouring elements and confirm the above conclusions. A semiempirical value for the omega 1 fluorescence yield of Cd is suggested.

Relative L-subshell ionisation cross sections for 0.15 to 10 MeV proton bombardment of Dy and Au

The L X-ray spectra of Dy and Au produced by proton impact have been measured over a broad range of projectile energies. From the intensities of characteristic lines the relative ionisation cross sections sigma i of the three L subshells Li were derived. The cross section ratios sigma 1/ sigma 2 and sigma 1/ sigma 3 vary significantly with projectile energy, attaining a maximum at low energies. This behaviour cannot be quantitatively described by available theoretical models.

Comment on 'L-subshell ionisation cross sections of xenon by electron impact near threshold region'

The authors draw attention to the fact that the work presented by Aydinol (1981) was the result of a collaboration between the authors and Aydinol, and that the paper was submitted for publication without the authors knowledge. The same work has since been presented, with Aydinol as a co-author, in Hippler et al. (1981). The data published by Hippler et al. (1981) differ from those given by Aydinol (1981) in that they include an important correction (of 5 to 20%) to the absolute subshell cross sections. This correction is due to the change in the detector efficiency in the energy range 4.1 to 5.4 keV.

L-subshell ionisation cross sections for Au and Pb by He+bombardment

The L X-ray production and subshell ionisation cross sections of Au and Pb have been measured by He+ bombardment of thick and thin targets in the energy range 0.8<or=E<or=3.0 MeV. These data are compared with the predictions of the plane-wave Born approximation (PWBA), the relativistic PWBA (PWBAR) and the Coulomb deflection corrected and perturbed stationary states relativistic PWBA (CPSSR) of Brandt and Lapicki (1979).

L-subshell ionisation cross sections of xenon by electron impact near threshold region

L-subshell ionisation cross sections for xenon atoms have been measured by electron impact at incident electron energies from about one to three times the ionisation threshold energy of these subshells. Ionisation cross sections for the L1, L2 and L3 subshells were deduced from the measured yields of characteristic Lgamma 2,3,4,4', Lgamma 1 and Lalpha 1,2 X-rays, using known values for the fluorescence yields, transition probabilities and Coster-Kronig factors. The cross sections have been made absolute by normalisation on the simultaneously measured bremsstrahlung intensity, using the known bremsstrahlung cross sections data of Pratt et al. (1977). For the energies investigated, the subshell ionisation cross sections were always larger than the theoretical cross sections of McGuire (1978). However, only at the lower energies is this discrepancy larger than the experimental error bars (25-40%).