Approximation For Electron Capture Research Articles

Reply to A Salin: Some remarks on strong-potential-Born expansions for ion-atom collisions

For original paper see A. Salin, Comment At. Mol. Phys., vol.26, p.1-11 (1991) Perturbation theories for Coulomb potentials are discussed. The equations of perturbation theory for such potentials cannot be solved by conventional Green function techniques, thus solutions employing more general methods are used. The author applies these more general methods to the distorted-wave strong-potential-Born (SPB) approximation for electron capture. The amplitudes are shown to be unique and well represented in a commonly used peaking approximation. An elementary discussion is given in response to recent criticisms of the theory.

K-shell x-ray production in 6C, 8O, 9F, 11Na, 12Mg, and 13Al by 0.5-8.0-MeV helium ions.

K-shell x-ray production cross sections are reported for incident $^{4}\mathrm{He}$ ions for elements with K-shell binding energies between 277 eV (C) and 1487 eV (Al). The data are compared with the first-order Born approximation (plane-wave Born approximation for direct ionization and Oppenheimer-Brinkman-Kramer approximation for electron capture) and to the energy loss and Coulomb deflection effects, perturbed stationary-state approximation with relativistic correction (ECPSSR) theory. The energy of the helium ions ranged from 0.5 to 6.0 MeV for ${\mathrm{He}}^{+}$ and 6.5 to 8.0 MeV for ${\mathrm{He}}^{2+}$. The targets used in these measurements were $_{6}\mathrm{C}$,${\mathrm{}}_{8}$O, $_{9}\mathrm{F}$, $_{11}\mathrm{Na}$, $_{12}\mathrm{Mg}$, and $_{13}\mathrm{Al}$. Except for a systematic overprediction of the data at the lower projectile velocities, the ECPSSR theory is found to fit the data. The first-order Born theory is found to fit the data at higher energy, but greatly overpredicts the data at low energy.

Electron transfer in nuclear reactions

The influence of nuclear reactions on atomic charge transfer in energetic ion-atom collisions is studied within a two-channel model for the reactions and the impulse approximation for electron capture. Large interference structures in the capture probability are found for the test reactions 12C(d,p)13C, 180(p,∝)15N, 19F(p,∝)160 and 32S(p,p′)32S.

M-shell X-ray production in gold, lead, bismuth, thorium and uranium by 70–200 keV protons

M-shell X-ray production cross sections have been measured for thin-foil targets (thickness in μg/cm 2) of 79Au (7.0), 82Pb (10.6), 83Bi (4.1), 90Th (7.9) and 92U (8.8) for 70–200 keV incident protons. These data are compared to other measurements at higher energies and to the first Born (plane-wave Born approximation for direct ionization and Oppenheimer-Brinkman-Kramers-Nikolaev approximation for electron capture) and ECPSSR (energy-loss and Coulomb deflection effects, perturbed stationary state approximation with relativistic correction for both direct ionization and electron capture) theories. The electron capture, included for completeness, contributed less than 1%. The ECPSSR underpredicts the data at all energies, while the first Born, which overpredicts the data, seems to approach agreement for low Z 2. The data follow a trend established in this laboratory by earlier work [R. Mehta et al., Phys. Rev. A26 (1982) 1883] at higher energies.

L-shell x-ray production cross sections of Ni, Cu, Ge, As, Rb, Sr, Y, Zr, and Pd by (0.25-2.5)-MeV protons.

L-shell x-ray production cross sections by /sub 1//sup 1/H/sup +/ ions are reported. The data are compared to the first Born approximation (plane-wave Born approximation for direct ionization and Oppenheimer-Brinkman-Kramers approximation for electron capture) and to the ECPSSR (energy-loss and Coulomb-deflection effects, perturbed stationary-state approximation with relativistic correction) theory. The energy of the protons ranged from 0.25 to 2.5 MeV in steps of 0.25 MeV. The targets used in these measurements were /sub 28/Ni, /sub 29/Cu, /sub 32/Ge, /sub 33/As, /sub 37/Rb, /sub 38/Sr, /sub 39/Y, /sub 40/Zr, and /sub 46/Pd. The first Born theory generally agrees with the data found in the literature at high energies and overpredicts them below 1.5 MeV. The ECPSSR predictions are in better agreement with experimental cross sections. At 0.25 MeV our data, however, are underestimated by this theory and tend to agree with the first Born approximation.