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 TIFR Mumbai Mar 9, 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

Guess who? ISIAC 2007 – Agios Nikolaos, Crete TIFR Mumbai Mar 9, 2015 Dancing to Greek music Enjoying Greek food + beer by the sea

The Mediterranean Crete

The Island of Crete 250 km 50 km Heraklion Area ~ 8200 km 2 (3200 mi 2 ) Population ~ winter > summer > summer Two mountains ~ 2450 m Heraklion population ~

Crete Heraklion

University of Crete - Heraklion UoC ~ 5000 students Physics Dept ~ 600 undergrads 50 grads 50 grads 30 faculty 30 faculty Physics Dept From my living room UoC campus Physics & Biology MedicalschoolUniversityHospital

Basic ion-atom collision processes TIFR Mumbai Mar 9, 2015 continuum K L M K capture K-M excitation E a - Auger energy KLM Auger transition e-e interaction Atomic Energy levels K ionization Atomic Structure Atomic Structure: q, Z p, Z t, E x, E a … Dynamics Collision Dynamics: b, V p, v t … Cross section Cross section: Few HCI: Few -electrons - simpler environment for testing theories Projectile spectroscopy: Projectile spectroscopy: Control # of electrons on ion by selecting its charge Special interest: Two-electron processes, e- correlations and deviations from the IPM M-K radiative transition ExEx VpVp ZpZp ZtZt b e-e- e-e- Ion-atom collision vtvt Projectile Ion Charge q+ Target Atom

Interest in Highly Charged Ions (HCI) Basic understanding of atomic collision processes (simpler systems, isoelectronic studies) High-Z HCI used to test QED corrections (spectroscopy) Astrophysical plasmas (Solar Corona etc.) Fusion research (ionization, recombination - plasma edge modeling, plasma-wall interactions, diagnostics - JET, ITER) Cometary X-ray emission (Charge-exchange of solar wind HCIs with cometary vapors) Radiation damage, Therapy of deep-seated localized tumors (energy loss, HCI bombardment of sensitive areas (brain, eye), narrow Bragg peak) HCI nano-structuring of surfaces (nano-hillock formation, potential sputtering) Guiding of HCI in insulator nano-capillaries Accelerator physics (source development, lifetime of particle beams in storage rings) Instrumentation R & D (spectrometers, position sensitive detectors, data acquisition) TIFR Mumbai Mar 9, 2015 TIFR Mumbai Mar 9, 2015

The 5.5 MV Tandem INPP/NCSRT “Demokritos” The 5.5 MV VdG Tandem delivered the first beams in THE ONLY ACCELERATOR FACILITY EXISTING IN GREECE Operation 2500 hrs/year, 65% external users Applied Research (40%) Materials, Cultural Heritage, Environmental studies Basic Research (60%) Nuclear Astrophysics Neutron Physics Nuclear Reactions on light systems Since 2014 also Atomic Physics!

Demokritos PHOTOS TIFR Mumbai Mar 9, 2015 Post stripper Tandem terminal 5.5 MV Demokritos Tandem HVE Accelerator

PHOTOS TIFR Mumbai Mar 9, 2015 Where beam line will exit the wall Aug Auger Projectile Spectroscopy Setup May 2014 New APAPES beam line for Atomic Physics

Projectile Spectroscopy Kinematic Broadening    F. Fremont et al 1997 Smallest at θ = 0 0

ZA PS Zero-degree Auger Projectile Spectroscopy TIFR Mumbai Mar 9, 2015 Best energy resolution obtained at 0 0 observation! Gas cell Ion beam electrons HDA PSD Lens

ZA PS Zero-degree Auger Projectile Spectroscopy TIFR Mumbai Mar 9, 2015 ZAPS experimental station Mar 5, 2015

15 Electron transfer in ion-atom collisions: F 7+ (1s 2 ) ion Target e- He-like ions F 6+ (1s 2 nl) ion F 6+ (1s 2 2s) ion Ground state TIFR Mumbai Mar 9, 2015

16 Electron transfer in ion-atom collisions: Electron transfer into metastable He-like ions: Target e-e-Analyzer F 7+ (1s2s 3 S) ion F 6+ (1s2s 3 Snl) ion F 7+ (1s 2 ) ion Auger e- emission F 7+ (1s 2 ) ion Target e- He-like ions F 6+ (1s 2 nl) ion F 6+ (1s 2 2s) ion Ground state TIFR Mumbai Mar 9, 2015

1s2s2p 3-electron spectrum resulting from e- capture to He-like beam 1.1 MeV/u F 7+ (1s 2 ) 75% F 7+ (1s2s 1 S) <1% F 7+ (1s2s 3 S) 24% τ 1/2 = 277 μs τ 1/2 = μs τ 1/2 = stable e- Analyzer F 6+ (1s2s 3 S2p) ion TIFR Mumbai Mar 9, 2015 Tanis et al PRL 2004

1.1 MeV/u He-like beam components: F 7+ (1s 2 ) 75% F 7+ (1s2s 1 S) <1% F 7+ (1s2s 3 S) 24% τ 1/2 = 277 μs τ 1/2 = μs τ 1/2 = ∞ - stable e- Analyzer F 6+ (1s2s 3 S2p) ion1s 2s 2p TIFR Mumbai Mar 9, 2015 Tanis et al PRL s2s2p 3-electron spectrum resulting from e- capture to He-like beam

Obtaining pure ground state beam contributions Benis et al PRA 2004 Practically pure ground state He-like beams Can be obtained using a gas stripper Inside the accelerator terminal Rather than a foil POST stripper Foilstripping Gasstripping Calculated (R-matrix) Ground state contribution Mixed state (1s 2, 1s2s 3 S) Spectrum 25% metastable TIFR Mumbai Mar 9, 2015

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! Practically pure ground state (1s 2 ) Spectrum < 3% metastable TIFR Mumbai Mar 9, 2015 Mixed state (1s 2, 1s2s 3 S) Spectrum 25% metastable

Gas terminal Gas terminalstripping Foil post stripping B 3+ Obtaining pure ground state beam contributions TIFR Mumbai Mar 9, 2015 C Foil Poststripper Ar Gas Post stripper Benis et al PRA 2002 Zamkov et al PRA 2001

Spin statistics for 2p capture to pure 1s2s 3 S He-like Initial States + 2p <1 % TIFR Mumbai Mar 9, 2015

Probability Spin statistics for 2p capture to 1s2s 3 S He-like Initial States + 2p 1s 2 TIFR Mumbai Mar 9, 2015

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

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

Obtaining pure metastable beam contributions Strohschein et al PRA 2008 TIFR Mumbai Mar 9, 2015

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! TIFR Mumbai Mar 9, 2015 Existence of 2 D line evidence of incomplete subtraction Strohschein et al PRA 2008 (WMU - Kalamazoo)

Obtaining pure metastable beam contributions Strohschein et al PRA 2008 Spin statistics Pure metastable state TIFR Mumbai Mar 9, 2015 So why the big discrepancy!? Ratio of 4 P/ 2 P

Supported also by observation for F 7+ beam Zouros et al. PRA 2008 Ratio of 4 P/ 2 P ~ for He ~ 0.5 – 5 for H 2 Clearly something Is the matter!? TIFR Mumbai Mar 9, 2015 Ratio largest at lowest collision energy

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 TIFR Mumbai Mar 9, 2015 WMU 1s2s 3 S

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 TIFR Mumbai Mar 9, 2015 Weird?!

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: TIFR Mumbai Mar 9, 2015 Cool! Slow Auger

Order Zouros et al, Phys. Rev. A Rapid Comm Cascade feeding 1s2s2p 4 P analysis TIFR Mumbai Mar 9, 2015 Slow Auger

TIFR Mumbai Mar 9, 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 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 ! TIFR Mumbai Mar 9, 2015 Fast Auger

Order Zouros et al, Phys. Rev. A Rapid Comm Cascade feeding 1s2s2p 2 P analysis TIFR Mumbai Mar 9, 2015 Fast Auger

Cascade feeding accounts for about 50% of the observed enhancement Similar results also presented for C 4+ So what is the rest due to? Strohschein PRA % Röhrbein et al PRA 2010 EXCELLENT QUESTION!

TIFR Mumbai Mar 9, 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 TIFR Mumbai Mar 9, 2015 Comparison Similar energy resolution

New results APAPES Our new results look very similar – except for 2-3 times larger 4 P! Comparison Reasonable since distance of target 5 times larger in APAPES - so more time to cascade ! Strohschein 2008

TIFR Mumbai Mar 9, 2015RatiocomparisonNewResults Give a bit Too Low 4 P/ 2 P Ratio!But much closer To 2!

TIFR Mumbai Mar 9, 2015 Consistency Check ratio 2 P+/ 2 P- However 2 P+/ 2 P- Ratio seems Good For all!

TIFR Mumbai Mar 9, 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

1/11/2007 APAPES ZAPS setup: Single stage 0 0 HDA with injection lens and 2-D position sensitive detector C 4+ Target gas n t ~10 12 #/cm 3 Differential Pumping ports Focusing and retardation Chamber pressure ~10 -7 Torr Overall efficiency gain ~ High Transmission ~ 90% Paracentric entry TIFR Mumbai Mar 9, 2015

PSD and DAQ Electronics TIFR Mumbai Mar 9, channelpreamp Acquired via collaboration with ATOMKI - Debrecen

PSD and DAQ Electronics TIFR Mumbai Mar 9, 2015

2-D image on PSD Projections PSD and DAQ TIFR Mumbai Mar 9, P4P4P4P Projection along energy axis X-proj Y-proj Sumsignal

APAPES s 0 =28.9cm Zero-degree Auger Projectile spectroscopy setups: 1s2s2p 4 P yield correction for long-life times TIFR Mumbai Mar 9, 2015 Our distance s 0 is about 5 times larger than in the WMU setup so its not Surprising that we measure More 4 P electrons! WMU s 0 =5.9cm s0s0s0s0

1.1 MeV/u F 7+ τ 1/2 = ns τ 3/2 = 7.88 ns τ 5/2 = 16.3 ns Zero-degree Auger Projectile spectroscopy setups: 1s2s2p 4 P yield correction for long-life times TIFR Mumbai Mar 9, 2015 WMU APAPES -12 MeV C 4+

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 MeV/u F 7+ τ 1/2 = ns τ 3/2 = 7.88 ns τ 5/2 = 16.3 ns WMU – two-stage parallel plate Analyser (2PPA) 1s2s2p 4 P metastable solid angle correction factor – WMU – two-stage parallel plate Analyser (2PPA) TIFR Mumbai Mar 9, 2015

APAPES Our distance s 0 is about 5 times larger than in the 2PPA setup so its not Surprising that we measure More 4 P electrons! 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

TIFR Mumbai Mar 9, 2015 SIMION Monte Carlo calculation: Correction factor for F 7+ and C 4+ Submitted to RSI 2015 APAPESKSU

TIFR Mumbai Mar 9, 2015 SIMION Monte Carlo calculation: Correction factor for 4 MeV B 3+

TIFR Mumbai Mar 9, MeV C 4+ SIMION correction factor calculation

Summary and Conclusion TIFR Mumbai Mar 9, 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 corrections to 4 P Tests of corrections 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 either Corrected 4 P/ 2 P ratio 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

APAPES Future TIFR Mumbai Mar 9, 2015 More measurements needed More measurements needed for different collision systems to for different collision systems to better check systematics (present APAPES) better check systematics (present APAPES) - He-like Ions: Li +, B 3+, C 4+, N 5+, O 6+, F 7+ - He-like Ions: Li +, B 3+, C 4+, N 5+, O 6+, F 7+ - Various targets: H 2, He, Ne, Ar, … - Various targets: H 2, He, Ne, Ar, … - Different energies: MeV/u - Different energies: MeV/u Install terminal gas stripper to also Install terminal gas stripper to also produce ground state He-like ions produce ground state He-like ions Install gas and foil post-stripper to enable Install gas and foil post-stripper to enable production of lower energy He-like ions production of lower energy He-like ions Investigate other 3-e spin statistics collision Investigate other 3-e spin statistics collision systems such as Be-like (ionization), systems such as Be-like (ionization), Li-like (excitation), etc. Li-like (excitation), etc. Experiment - Measurements:

APAPES Future TIFR Mumbai Mar 9, 2015 Tests of solid angle corrections to 4 P (use SIMION Monte Carlo approach on 2PPA results) Tests of solid angle corrections to 4 P (use SIMION Monte Carlo approach on 2PPA results) Follow up cascade calculations for all measured collision systems Follow up cascade calculations for all measured collision systems Include possible alignment due to capture Include possible alignment due to capture Can someone please calculate Can someone please calculate Pauli Exchange Interaction? Pauli Exchange Interaction? Theory - Simulation: Open to NEW collaborations!

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) TIFR Mumbai Mar 9, 2015

APAPES APAPES important participants TIFR Mumbai Mar 9, 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 TIFR Mumbai Mar 9, 2015

The end thank you for listening I thank Dr. Lokesh Tribedi for inviting me More info? Please Contact me: TIFR Mumbai Mar 9, 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