1. HIGH RESOLUTION AUGER PROJECTILE ELECTRON SPECTROSCOPY OF LI-LIKE IONS PRODUCED BY ELECTRON CAPTURE OF HE-LIKE IONS IN COLLISIONS WITH GASEOUS TARGETS HIGH RESOLUTION AUGER PROJECTILE ELECTRON SPECTROSCOPY OF LI-LIKE IONS PRODUCED BY ELECTRON CAPTURE OF HE-LIKE IONS IN COLLISIONS WITH GASEOUS TARGETS CDAMOP Delhi Mar 12, 2015 Theo J.M. Zouros Dept. of Physics, University of Crete, Heraklion, Crete, GREECE Atomic Collisions & Electron Spectrometry Laboratory & Institute of Nuclear and Particle Physics, Demokritos, Athens

2. Focus on Focus on CDAMOP Delhi Mar 12, 2015 Non-statistical production of 1s2s2p 4 P and 1s2s2p 2 P states by e- capture to the 1s2s 3 S state: Non-statistical production of 1s2s2p 4 P and 1s2s2p 2 P states by e- capture to the 1s2s 3 S state: A persisting puzzle! Accelerator-based atomic physics topic (ion-atom collisions)

3. 1s2s2p 3-electron spectrum resulting from e- capture to He-like beam e- Analyzer F 6+ (1s2s 3 S2p) ion CDAMOP Delhi Mar 12, 2015 2P±2P±2P±2P± 4P4P4P4P

4. C 4+ (1s 2 ) 75% C 4+ (1s2s 3 S) 20% τ 1/2 = 20.6 ms τ 1/2 = ∞ - stable e- Analyzer CDAMOP Delhi Mar 12, 2015 1s2s2p 3-electron spectrum resulting from e- capture to He-like beam F 6+ (1s2s 3 S2p) ion 2P±2P±2P±2P± 4P4P4P4P Interest in ratio 4 P/ 2 P He-like beam components: C 4+ (1s2s 1 S) 5% τ 1/2 = 3 μs

5. Obtaining pure ground state beam contributions Foilstripping Gasstripping CDAMOP Delhi Mar 12, 2015 Mixed state (1s 2, 1s2s 3 S) Spectrum 25% metastable Theory

6. Obtaining pure ground state beam contributions Benis et al PRA 2004 Foilstripping Gasstripping Gas stripping at lower energies Produces He-like ions mostly in ground state! CDAMOP Delhi Mar 12, 2015 Mixed state (1s 2, 1s2s 3 S) Spectrum 25% metastable TheoryPractically pure ground state (1s 2 ) Spectrum < 3% metastable

7. CDAMOP Delhi Mar 12, 2015 Ratio 4 P/ 2 P Independent of most Independent of most instrumental parameters instrumental parameters (i.e. detector efficiency, number of ions, (i.e. detector efficiency, number of ions, target pressure, etc.) target pressure, etc.) Obey spin statistics Obey spin statistics Unexpected value could reveal Unexpected value could reveal existence of underlying existence of underlying processes processes

8. Spin statistics for 2p capture to pure 1s2s 3 S He-like Initial States + 2p CDAMOP Delhi Mar 12, 2015

9. Probability Spin statistics for 2p capture to 1s2s 3 S He-like Initial States + 2p 1s 2 CDAMOP Delhi Mar 12, 2015

10. Probability Spin statistics for 2p capture to 1s2s 3 S Li-like Final States He-like Initial States + 2p 1s 2

11. Probability Spin statistics for 2p capture to 1s2s 3 S Li-like Final States Spin recoupling He-like Initial States + 2p 1s 2 4 P : 2 P - : 2 P + Finalbreakdown 2:1

12. CDAMOP Delhi Mar 12, 2015 Ratio 4 P/ 2 P Expected ratio from spin statistics After subtraction of Ground state “contamination” 4 P/ 2 P = 2 4 P/ 2 P = 2

13. Obtaining pure metastable beam contributions Strohschein et al PRA 2008 CDAMOP Delhi Mar 12, 2015

14. Obtaining pure metastable beam contributions Pure metastable state Mixed – Norm. Ground state = In 2008 Tanis and company Used this technique to measure both mixed and ground state contributions in C 4+ beams The spectra were then normalized and subtracted leaving the pure metastable component only! CDAMOP Delhi Mar 12, 2015 Existence of 2 D line evidence of incomplete subtraction Strohschein et al PRA 2008 (WMU - Kalamazoo)

15. Obtaining pure metastable beam contributions Strohschein et al PRA 2008 Spin statistics Pure metastable state CDAMOP Delhi Mar 12, 2015 So why the big discrepancy!? Ratio of 4 P/ 2 P

16. First explanation: Pauli exchange interaction? An electron with antialigned spin An electron with antialigned spin can populate either the 1s, 2s or can populate either the 1s, 2s or 2p levels, in the later case giving 2p levels, in the later case giving rise to the 2 P + state rise to the 2 P + state Cannot form 1s2s2p 4 P Cannot form 1s2s2p 4 P CDAMOP Delhi Mar 12, 2015 WMU 1s2s 3 S

17. Pauli exchange interaction A target electron with spin aligned to the spin of the 1s projectile: A target electron with spin aligned to the spin of the 1s projectile: a) can be captured into the 2p a) can be captured into the 2p directly to form the 1s2s2p 4 P directly to form the 1s2s2p 4 P b) CANNOT be captured into the 1s b) CANNOT be captured into the 1s (or 2s) due to Pauli exclusion. (or 2s) due to Pauli exclusion. Tanis et al PRL2004 The Pauli Exchange Interaction is reminiscent of the Transfer-Excitation mechanism, but with two identical electrons doing the Transfer and the Excitation! - Rather puzzling and difficult to calculate (not possible to date!) - Rather puzzling and difficult to calculate (not possible to date!) New idea: So instead it interacts with the 1s (or 2s) e- via a Pauli Exchange Interaction with one e- transferred to the 2p forming additional 4 P states CDAMOP Delhi Mar 12, 2015 Weird?!

18. Tanis et al considered capture only to n=2 Significant capture to higher n=3-7 indicated by our CDW calculations Overlooked channel: Radiative cascade Feeding Radiative cascade Feeding! nl Alternative hypothesis: Cascade feeding

19. Order Cascade feeding 1s2s2p 4 P analysis Quartet  Doublet NOT allowed! Quartet  Quartet allowed! Strong cascade feeding of 1s2s2p 4 P ! For a state p: transitions depopulating populating E1Selection Rules: CDAMOP Delhi Mar 12, 2015 Cool! Slow Auger

20. Order Zouros et al, Phys. Rev. A Rapid Comm. 2008 Cascade feeding 1s2s2p 4 P analysis CDAMOP Delhi Mar 12, 2015 Slow Auger

21. CDAMOP Delhi Mar 12, 2015 But wait a minute! Shouldn’t the cascades also feed the 2 P states too Thus also enhancing the denominator of the 4 P/ 2 P ratio? Indeed! But …

22. Order Cascade feeding 1s2s2p 2 P analysis Same E1 selection rules! However now Auger transitions to ground state much stronger! They rapidly deplete higher lying levels! Minimal cascade feeding of 1s2s2p 2 P ! CDAMOP Delhi Mar 12, 2015 Fast Auger

23. Order Zouros et al, Phys. Rev. A Rapid Comm. 2008 Cascade feeding 1s2s2p 2 P analysis CDAMOP Delhi Mar 12, 2015 Fast Auger

24. This selective Cascade feeding mechanism accounts for about 50% of the observed enhancement Similar results also presented for C 4+ So what is the rest due to? Strohschein et al PRA 2008 70% Röhrbein, Kirchner, Fritzsche PRA 2010 EXCELLENT QUESTION!

25. CDAMOP Delhi Mar 12, 2015 In progress: Installation of terminal gas stripper to produce ground state beams Installation of terminal gas stripper to produce ground state beams Installation of post strippers (foil and gas) to produce He-like ions at lower energies Installation of post strippers (foil and gas) to produce He-like ions at lower energies Investigation of the systematics of the 4 P/ 2 P ratio in an Isoelectronic sequence study He Li +, B 3+, C 4+, N 5+, O 6+, F 7+ 0.1-2 Investigation of the systematics of the 4 P/ 2 P ratio in an Isoelectronic sequence study using He-like ions from Li +, B 3+, C 4+, N 5+, O 6+, F 7+ in the 0.1-2 MeV/u different targets H 2, He, Ne, Ar Use different targets such as H 2, He, Ne, Ar Ideally suited to the Demokritos tandem accelerator energy range of 0.8-5 MV. 2013 - APAPES Proposal granted!

26. New results 2014-2015APAPES Strohschein 2008 CDAMOP Delhi Mar 12, 2015 Comparison Similar energy resolution

27. New results 2014-2015APAPES Our new results look very similar – except for 2-3 times larger and wider 4 P!??? Comparison Strohschein 2008

28. CDAMOP Delhi Mar 12, 2015RatiocomparisonNewResults Give much Lower 4 P/ 2 P Ratio!But much closer To 2! (after correction for solid angle effect in 4 P due to its long life time)

29. CDAMOP Delhi Mar 12, 2015 Consistency Check ratio 2 P+/ 2 P- However 2 P+/ 2 P- Ratio seems Good For all!

30. CDAMOP Delhi Mar 12, 2015 New calculations are needed to evaluate capture and cascade contributions for all measured collision systems More New results 2014-2015 New targets Higher Energy – 18 MeV

31. Zero-degree Auger Projectile spectroscopy setups: 1s2s2p 4 P yield correction for long-life times CDAMOP Delhi Mar 12, 2015 WMU APAPES -12 MeV C 4+ 28.9cm 1.1 MeV/u F 7+ τ 1/2 = 0.735 ns τ 3/2 = 7.88 ns τ 5/2 = 16.3 ns 5.8cm

32. Important Yield correction Factor (x 2.5) 1.1 MeV/u For C 4+ 4 P correction factors: 7.3, 8.8, 10.2 for 6, 9, 12 MeV Strohschein PRA 2008 WMU – two-stage parallel plate Analyser (2PPA) 1s2s2p 4 P metastable solid angle correction factor – WMU – two-stage parallel plate Analyser (2PPA) CDAMOP Delhi Mar 12, 2015 1.1 MeV/u F 7+ τ 1/2 = 0.735 ns τ 3/2 = 7.88 ns τ 5/2 = 16.3 ns 5.8cm

33. CDAMOP Delhi Mar 12, 2015 APAPES Calculated by SIMION Monte Carlo 12 MeV C 4+ APAPESHemispherical Deflector Analyzer HDA) 1s2s2p 4 P metastable solid angle correction factor – APAPES Hemispherical Deflector Analyzer (HDA) 28.9cm

34. Summary and Conclusion CDAMOP Delhi Mar 12, 2015 More measurements still needed More measurements still needed for different collision systems to for different collision systems to better check systematics (APAPES) better check systematics (APAPES) Follow up cascade calculations Follow up cascade calculations Tests of solid angle correction factors to 4 P Tests of solid angle correction factors to 4 P Can someone please calculate the Can someone please calculate the Pauli Exchange Interaction? Pauli Exchange Interaction? Controversy still remains: Controversy still remains: Corrected 4 P/ 2 P ratio for C 4+ either Corrected 4 P/ 2 P ratio for C 4+ either too large (WMU) or too small (APAPES)! New results even more controversial! New results even more controversial! Still preliminary – need to be checked further Still preliminary – need to be checked further

35. APAPES APAPES Main team Dept. of Physics, Univ. of Crete, Heraklion Dept. of Physics, Univ. of Crete, Heraklion Theo Anastasios Ioannis Angelos Theo Anastasios Ioannis Angelos Zouros Dimitriou Madesis Laoutaris Zouros Dimitriou Madesis Laoutaris (Prof & PI) (PostDoc) (PhD student) (MS student) (Prof & PI) (PostDoc) (PhD student) (MS student) CDAMOP Delhi Mar 12, 2015

36. APAPES APAPES important participants CDAMOP Delhi Mar 12, 2015 Manolis Bela Omer Genoveva Jose Manolis Bela Omer Genoveva Jose Benis Sulik Sise Martinez-Lopez Paulo Santos Benis Sulik Sise Martinez-Lopez Paulo Santos (Prof) (Prof) (Prof) (Prof) (Prof) (Prof) (Prof) (Prof) (Prof) (Prof) Dept of Physics Univ of Ioannina GreeceATOMKIDebrecenHungary Univ of Isparta Turkey Dept Fisica Aplicada Madrid, Spain Dept de Fisica Univ Nova de Lisboa Portugal CPO simulations Zoom lenses AtomicStructurecalculations SpirosDoukas U. Ioannina SIMION Measurements

37. APAPES APAPES Support Team 5MV Tandem, Institute of Nuclear and Particle Physics 5MV Tandem, Institute of Nuclear and Particle Physics NCSRT Demokritos NCSRT Demokritos Dr. Sotiris Dr. Tasos Dr. Michalis Miltos Theo Harissopulos Lagoyannis Axiotis Andrianis Mertzimekis (Director) (Res.) (Res.) (Accel. Eng.) (Prof.) Univ. of Athens CDAMOP Delhi Mar 12, 2015

38. The end thank you for listening I thank the organizers for inviting me More info? Please Contact me: tzouros@physics.uoc.gr CDAMOP Delhi Mar 12, 2015 Acknowledgement: This research has been co-financed by the European Union (European Social Fund ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) Research Funding Program: THALES. Investing in knowledge society through the European Social Fund, grant number MIS 377289.