Experimental cross sections for electron-impact ionization and electron-ion recombination

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

2. Experimental workwithinthe CRP was performedby 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 • Overview • 2. Results on electron-impact ionization of ions • Xeq+ , q=1,2,…,15 • 3. Results on electron-ion recombination • Fe13+, Fe14+, Si3+

4. Giessenworkplannedforthepresent CRP cross sections for electron-impact single and multiple ionization of ions especially Xeq+ ions q=1,2,…,15 and possibly also for Snq+ ions q=1,2,… rate coefficients for radiative and dielectronic recombinationof ions especially Fe8+, Fe13+, Fe14+, Fe16+

5. Electron-ioncrossed-beamssetupat IAMP Versatile apparatus for studying atomic collisions (additional beamlines not shown)

6. Electron-ion beam crossingregion

7. Xenon ions produced by ECR source 2003

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

9. Electron-ion beam crossingregion

10. Measurement ofcrosssections absolute high precision

11. Test experimentwith Li+ (1s2) ions

12. Ion production: Li+ (1s2) and Li+ (1s2s) ions Electron cyclotron resonance (ECR) ion source Li, LiF Li 2+ ion yield metallic Li evaporated threshold at 16.6 eV Depending on source operation there may be metastable ions in the primary ion beam

13. Effectsofmetastableions on crosssections

14. Unknownfractionsof metastableions in parentionbeams 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 Xe6+

16. Measurements on single ionization of Xe6+

17. Metastable Xe6+ 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 Xe10+ ions

21. Xenon ions produced by ECR source 2007

22. Xenon ions produced by ECR source 2007 picoAmperes of isotope-resolved Xe27+ ions

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

24. Electron-ion collisions at heavy-ion storage rings recombination 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 Fe17+ Fe18+ Fe20+ Fe19+ Fe21+ Fe22+ Columbia-Astrophysics Laboratory Justus-Liebig-Universität Giessen Max-Planck-Institut für Kernphysik

27. Recombinationof Fe13+ionsfinalized: 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. Recombinationof Fe13+ions : Rydbergseries 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. Recombinationof Fe13+ions : hugeresonancesatverylowenergies 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. Recombinationof Fe13+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 Fe14+: plasma rate coefficients experiment, minus 2 experiment, all effect of high-n extrapolation MCBP theory RR, Arnaud&Raymond recommended Arnaud&Raymond recommended Netzer modified 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)

32. 3 → 3 DR of Si3+: 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 Xeq+ ions, q=1,2,…,15,… and of Snq+ 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 Fe13+ and Fe14+ have been obtained and published. Data on Si3+have been finalized and are being published.Preliminary data are available for Fe7+ and Fe8+. Their analysis is underway.

34. Outlook Electron-impact ionization of ions: Complete cross section measurements for single and multiple ionization of Xeq+ ions, q=1,2,…,15,… and of Snq+ ions, q=1,2,… Dielectronic recombination: Finalize data analysis and obtain resonance strengths and plasma rate coefficients for Fe7+ and Fe8+. Extend the series to other ions in the iron iso-nuclear sequence.