Electron-impact-excitation cross sections of hydrogenlike ions
- Faculty of Physics, Weizmann Institute of Science, Rehovot 76100 (Israel)
- P. N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow 117924 (Russia)
- Electronic Structure of Materials Centre, School of Physical Sciences, The Flinders University of South Australia, G.P.O. Box 2100, Adelaide 5001 (Australia)
- Churchill College, Cambridge CB3 0DS (United Kingdom)
Convergent close-coupling (CCC) and Coulomb-Born with exchange and normalization (CBE) methods are used to study electron-impact excitation of hydrogenlike ions. The nl{r_arrow}n{sup {prime}}l{sup {prime}} cross sections demonstrate (i) good agreement between the CCC and CBE results, (ii) a scaling over ion nuclear charge z, (iii) a domination of the dipole (l{sup {prime}}=l{plus_minus}1) contributions in total n{r_arrow}n{sup {prime}} cross sections, and (iv) significant effect of electron exchange in the energy range x{lt}3 (here x is the ratio of the incident electron kinetic energy {var_epsilon} to the transition energy E{sub n,n{sup {prime}}}). For ions with z{gt}5 the n{r_arrow}n{sup {prime}} cross sections obtained in the CCC and CBE approximations agree with each other to better than 10{percent} for any x. An accuracy of the cross sections scaling over z{sup 4} depends on z: for z=6{endash}18 the scaling is accurate to better than 10{percent} (quantitative analysis is done for n{sup {prime}}{lt}7), for ions with z{lt}6 the cross sections deviate from the z{sup 4} scaling more significantly (at x about unity). The n{r_arrow}n{sup {prime}} cross sections are presented by a formula which fits our CCC and CBE results with an accuracy to better than 10{percent} (for transitions with n{lt}n{sup {prime}}{lt}7 in ions with z{gt}5). The new Gaunt factor G(x) suggested for the widely used Van Regemorter formula [Astrophys. J. {bold 136}, 906 (1962)] makes this formula accurate to better than 50{percent} in the x{gt}3 range and to better than 20{percent} in the x{gt}100 range. It is shown that the semiempirical formula by Vainshtein, Sobelman, and Yukov provides an accuracy to better than 50{percent} for any incident electron energy. For x{lt}2 this formula is accurate to better than 30{percent}. These accuracy assessments are based on a comparison with our CCC and CBE results. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 459837
- Journal Information:
- Physical Review A, Journal Name: Physical Review A Journal Issue: 1 Vol. 55; ISSN 1050-2947; ISSN PLRAAN
- Country of Publication:
- United States
- Language:
- English
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