1. Experimental cross sections for electron-impact ionization and electron-ion recombination Research Coordination Meeting, IAEA CRP, Vienna, 26-28 September 2007 Alfred Müller Institut für Atom- und Molekülphysik

2. Experimental work within the CRP was performed by Stefan Schippers Eike Schmidt Alexander Borovik jr. Dietrich Bernhardt Mohammad Gharaibeh (visting from Irbid, Jordan) Carsten Brandau (now GSI) Sebastian Böhm (now Stockholm) A.M. IAMP, Giessen A. Wolf, M. Grieser, J. Hoffmann, A. S. Jaroshevich, C. Krantz, D. A. Orlov, R. Repnow, F. Sprenger MPI-K, Heidelberg D. W. Savin, M. Lestinsky, D. Lukić, M. Schnell Columbia University, Astronomy & Astrophysics, New York

3. Outline 1.Overview 2. Results on electron-impact ionization of ions Xe q+, q=1,2,…,15 3. Results on electron-ion recombination Fe 13+, Fe 14+, Si 3+

4. cross sections for electron-impact single and multiple ionization of ions especially Xe q+ ions q=1,2,…,15 and possibly also for Sn q+ ions q=1,2,… rate coefficients for radiative and dielectronic recombination of ions especially Fe 8+, Fe 13+, Fe 14+, Fe 16+ Giessen work planned for the present CRP

5. Versatile apparatus for studying atomic collisions (additional beamlines not shown) Electron-ion crossed-beams setup at IAMP

6. Electron-ion beam crossing region

7. Xenon ions produced by ECR source 2003

8. Measurement of absolute cross sections Requirement for the measurement of cross sections: Beam density distributions → beam overlap → formfactor

9. Electron-ion beam crossing region

10. Measurement of cross sections absolute high precision

11. Test experiment with Li + (1s 2 ) ions

12. Ion production: Li + (1s 2 ) and Li + (1s2s) ions Electron cyclotron resonance (ECR) ion source Li, LiF Depending on source operation there may be metastable ions in the primary ion beam Li 2+ ion yield metallic Li evaporated threshold at 16.6 eV

13. Effects of metastable ions on cross sections

14. Unknown fractions of metastable ions in parent ion beams In some cases the metastable content of the primary ion beam can be controlled More often, when several metastable states contribute, it is difficult to assess their contents in the parent ion beam A possible way out: store parent ions in a storage ring for sufficiently long times prior to the measurement and let excited states decay $ $

15. Measurements on single ionization of Xe 6+

17. Metastable Xe 6+ states in the parent ion beam „Cold“ Penning ion source and „hot“ ECR ion source

18. Steps and resonance peaks in single ionization Griffin et al, 1983

19. Single ionization using beams from ECR sources

20. Electron-impact ionization of Xe 10+ ions

21. Xenon ions produced by ECR source 2007

22. Xenon ions produced by ECR source 2007 picoAmperes of isotope-resolved Xe 27+ ions

23. Single ionization of Xe q+ ions: overview A. Borovik jr., M. Gharaibeh, S. Schippers, and A. Müller, 2007

24. Electron-ion collisions at heavy-ion storage rings ionization recombination

25. Storage ring TSR at Max-Planck-Institut für Kernphysik, Heidelberg, where metastables die out

26. Dielectronic recombina- tion of Fe L- shell ions: a joint US-German project for astrophysics Fe 22+ Fe 19+ Fe 17+ Fe 18+ Fe 20+ Fe 21+ Columbia- Astrophysics Laboratory Justus-Liebig- Universität Giessen Max-Planck- Institut für Kernphysik

27. Recombination of Fe 13+ ions finalized: overview E. W. Schmidt, S. Schippers, A. Müller, M. Lestinsky, F. Sprenger, M. Grieser, R. Repnow, A. Wolf, C. Brandau, D. Lukić, M. Schnell, D. W. Savin, Astrophys. J. 641, L157 (2006)

28. Recombination of Fe 13+ ions : Rydberg series E. W. Schmidt, S. Schippers, A. Müller, M. Lestinsky, F. Sprenger, M. Grieser, R. Repnow, A. Wolf, C. Brandau, D. Lukić, M. Schnell, D. W. Savin, Astrophys. J. 641, L157 (2006)

29. Recombination of Fe 13+ ions : huge resonances at very low energies E. W. Schmidt, S. Schippers, A. Müller, M. Lestinsky, F. Sprenger, M. Grieser, R. Repnow, A. Wolf, C. Brandau, D. Lukić, M. Schnell, D. W. Savin, Astrophys. J. 641, L157 (2006)

30. Recombination of Fe 13+ ions : plasma rate coefficients E. W. Schmidt, S. Schippers, A. Müller, M. Lestinsky, F. Sprenger, M. Grieser, R. Repnow, A. Wolf, C. Brandau, D. Lukić, M. Schnell, D. W. Savin, Astrophys. J. 641, L157 (2006)

31. 3 → 3 DR of Fe 14+ : plasma rate coefficients D. Lukić, M. Schnell, D. W. Savin C. Brandau, E. W. Schmidt, S. Böhm, A. Müller, S. Schippers, M. Lestinsky, F. Sprenger, A. Wolf, Z. Altun, N. R. Badnell, Astrophys. J. 664, 1244 (2007) experiment, all experiment, minus 2 Arnaud&Raymond recommended Netzer modified MCBP theory RR, Arnaud&Raymond recommended effect of high-n extrapolation

32. 3 → 3 DR of Si 3+ : plasma rate coefficients E. W. Schmidt, D. Bernhardt, A. Müller, S. Schippers, S. Fritzsche, J. Hoffmann, A. S. Jaroshevich, C. Krantz, M. Lestinsky, D. A. Orlov, A. Wolf, D. Lukić, D. W. Savin, Phys. Rev. A 2007, in the press

33. Summary Electron-impact ionization of ions: Cross sections for single and multiple ionization of Xe q+ ions, q=1,2,…,15,… and of Sn q+ ions, q=1,2,… are being measured in Giessen and analysis of the experimental results is underway. (( Dielectronic recombination: resonance strengths and plasma rate coefficients are determined in high-resolution storage ring experiments. Data for Fe 13+ and Fe 14+ have been obtained and published. Data on Si 3+ have been finalized and are being published. Preliminary data are available for Fe 7+ and Fe 8+. Their analysis is underway.

34. Outlook Electron-impact ionization of ions: Complete cross section measurements for single and multiple ionization of Xe q+ ions, q=1,2,…,15,… and of Sn q+ ions, q=1,2,… Dielectronic recombination: Finalize data analysis and obtain resonance strengths and plasma rate coefficients for Fe 7+ and Fe 8+. Extend the series to other ions in the iron iso-nuclear sequence.