I NVESTIGATION OF THE N ON - STATISTICAL PRODUCTION RATIO OF 1 S 2 S 2 P 4 P AND 1 S 2 S 2 P 2 P STATES BY e- CAPTURE TO THE 1 S 2 S 3 S STATE OF He- LIKE IONS : A PROGRESS REPORT I NVESTIGATION OF THE N ON - STATISTICAL PRODUCTION RATIO OF 1 S 2 S 2 P 4 P AND 1 S 2 S 2 P 2 P STATES BY e- CAPTURE TO THE 1 S 2 S 3 S STATE OF He- LIKE IONS : A PROGRESS REPORT XXIV ISIAC Barcelona July 19-21, 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

ISIAC Barcelona July 19-21, 2015 Also want to do Li +, N 5+, O 6+ He-like Ion Beams: Gas targets 0.1 – 2 MeV/u Production of 1s2s2p 4 P and 1s2s2p 2 P states by e- capture to the 1s2s 3 S state of He-like the 5 MV Tandem of Demokritos Athens, Greece APAPES project (

1s2s2p 3-electron spectrum resulting from e- capture to He-like beam e- Analyzer F 6+ (1s2s 3 S2p) ion ISIAC Barcelona July 19-21, P±2P±2P±2P± 4P4P4P4P Interest in ratio 4 P/ 2 P

ISIAC Barcelona July 19-21, 2015 What’s in a Ratio? R= 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

ISIAC Barcelona July 19-21, 2015 Ratio R= 4 P/ 2 P Expected ratio from spin statistics After subtraction of Ground state “contamination” R= 4 P/ 2 P = 2 R= 4 P/ 2 P = 2 2 P + / 2 P- = 3 Additional new check: 2 P= 2 P P-

Obtaining pure metastable beam contributions Strohschein et al PRA 2008 Spin statistics Pure metastable state ISIAC Barcelona July 19-21, 2015 So why the big discrepancy!? Ratio of 4 P/ 2 P WMU

First explanation: Pauli exchange interaction? ISIAC Barcelona July 19-21, 2015 WMU Alternative hypothesis: Cascade feeding UoC

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

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: ISIAC Barcelona July 19-21, 2015 Cool! Slow Auger

New plots based on the work of Röhrbein et at Phys. Rev. A 2010 Cascade feeding 1s2s2p 4 P analysis ISIAC Barcelona July 19-21, 2015 Slow Auger Order c0 c1c2 c0 c1 c2 σ 4 P(t) t (s) Strong cascade Feeding! For t > s 1 MeV/u C 4+ + He

ISIAC Barcelona July 19-21, 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 …

Order c0 c1c2 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 ! ISIAC Barcelona July 19-21, 2015 Fast Auger

Order c0 c1c2 Cascade feeding 1s2s2p 2 P analysis ISIAC Barcelona July 19-21, 2015 Fast Auger New plots based on the work of Röhrbein et at Phys. Rev. A 2010 σ 2 P(t) t (s) c0 c1 c2 No cascade Feeding! State depleted for t > s 1 MeV/u C 4+ + He

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 % Röhrbein, Kirchner, Fritzsche PRA 2010 EXCELLENT QUESTION!

ISIAC Barcelona July 19-21, 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 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 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 MV APAPES Proposal granted!

New results APAPES Strohschein 2008 ISIAC Barcelona July 19-21, 2015 Comparison Similar energy resolution

ISIAC Barcelona July 19-21, 2015 New calculations are needed to evaluate capture and cascade contributions for all measured collision systems More New results New targets Higher Energy – 18 MeV

Zero-degree Auger Projectile spectroscopy setups: 1s2s2p 4 P yield correction for long-life times ISIAC Barcelona July 19-21, 2015 WMU 1 MeV/u C 4+ τ 1/2 = 2.8 ns τ 3/2 = 7.3 ns τ 5/2 = 120 ns 5.8cm APAPES -12 MeV C cm

Zero-degree Auger Projectile spectroscopy setups: 1s2s2p 4 P yield correction for long-life times ISIAC Barcelona July 19-21, 2015 WMU 1 MeV/u C 4+ τ 1/2 = 2.8 ns τ 3/2 = 7.3 ns τ 5/2 = 120 ns 5.8cm For C 4+ 1s2s2p 4 P correction factors: 7.3, 8.8, 10.2 for 6, 9, 12 MeV Strohschein PRA 2008 c0

WMU – two-stage parallel plate Analyser (2PPA) 1s2s2p 4 P metastable solid angle correction factor – WMU – two-stage parallel plate Analyser (2PPA) ISIAC Barcelona July 19-21, PPAentry Lost e- Detected e- Comparison for c0 and c2 z (mm) – distance from target z = V p t dN/dz

WMU – two-stage parallel plate Analyser (2PPA) 1s2s2p 4 P metastable solid angle correction factor – WMU – two-stage parallel plate Analyser (2PPA) ISIAC Barcelona July 19-21, 2015 No cascade correction New point! With cascades c2 correction Röhrbein, Kirchner, Fritzsche PRA 2010

Summary and Conclusions ISIAC Barcelona July 19-21, 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? c2 Cascades included c2 Cascades included in the solid angle correction factor in the solid angle correction factor Now Corrected 4 P/ 2 P ratio for C 4+ Now Corrected 4 P/ 2 P ratio for C 4+ in much better agreement with theory! in much better agreement with theory!

ISIAC Barcelona July 19-21, 2015 Tom Kirchner York University Toronto, Ontario, Canada In April 2015 joined the APAPES collaboration THEORY – Capture calculations and Analytic Cascade formulation Curtis, AJP 1968

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) ISIAC Barcelona July 19-21, 2015

APAPES APAPES important participants ISIAC Barcelona July 19-21, 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

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 ISIAC Barcelona July 19-21, 2015

The end thank you for listening More info? Please Contact me: ISIAC Barcelona July 19-21, 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 Recent publication: Doukas et al. RSI 84 (2015)