69th NUPECC meeting October 8, Electron transfer into metastable He-like ions: Investigation of non-statistical population mechanisms Theo J.M. Zouros Dept. of Physics, University of Crete Heraklion, Crete, GREECE A proposal for atomic collision experiments at the Demokritos TANDEM

3-electron spectrum from collisions of 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

3-electron spectrum from collisions of 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

Spin statistics for 2p capture to pure 1s2s 3 S He-like Initial States + 2p <1 %

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

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

Obtaining pure metastable beam contributions Strohschein et al PRA 2008 Pure metastable = Mixed - Ground

Obtaining pure metastable beam contributions Strohschein et al PRA 2008 Spin statistics So why the big discrepancy???

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

Pauli exchange interaction An electron with a spin aligned An electron with a spin aligned with the spin of the 1s projectile: with the spin of the 1s projectile: a) can be captured into the 2p a) can be captured into the 2p directly to form the 4 P state directly to form the 4 P state 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. So instead it interacts with the 1s So instead it interacts with the 1s (or 2s) via a (or 2s) via a Pauli Exchange Interaction Pauli Exchange Interaction so that one of them is transferred to so that one of them is transferred to the 2p forming additional 4 P states the 2p forming additional 4 P states Tanis et al PRL2004

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! nl

Order Cascade feeding 1s2s2p 4 P analysis Quartet Doublet NOT allowed! Quartet Quartet allowed! Strong cascade feeding of 1s2s2p 4 P

Order Zouros et al, Phys. Rev. A Rapid Comm Cascade feeding 1s2s2p 4 P analysis

Order Cascade feeding 1s2s2p 2 P analysis All transitions allowed! However Auger transitions much stronger! They rapidly deplete higher lying levels! NO effective cascade feeding!

Order Zouros et al, Phys. Rev. A Rapid Comm Cascade feeding 1s2s2p 2 P analysis

Cascade feeding accounts for about 50% of the observed enhancement Final verdict So what is the rest due to?

Proposal Isoelectronic sequence study using He-like ions from Li + to F 7+ in the MeV/u where capture is strongest and effect seems to be the largest

Proposal Isoelectronic sequence study using He-like ions from Li + to F 7+ in the MeV/u where capture is strongest and effect seems to be the largest Ideally suited to the Demokritos tandem energy range of MV.

Proposal Isoelectronic sequence study using He-like ions from Li + to F 7+ in the MeV/u where capture is strongest and effect seems to be the largest. Ideally suited to the Demokritos tandem energy range of MV Needed: terminal gas stripper to produce pure ground state He-like beams – low intensity beams ~1-10nA

Proposal Isoelectronic sequence study using He-like ions from Li + to F 7+ in the MeV/u where capture is strongest and effect seems to be the largest. Ideally suited to the Demokritos tandem energy range of MV Needed: terminal gas stripper to produce pure ground state He-like beams – low intensity beams ~1-10nA Will use electron hemispherical spectrometer with position sensitive detector for high quality statistics ideally suited for working with low intensity beams

Proposal Isoelectronic sequence study using He-like ions from Li + to F 7+ in the MeV/u where capture is strongest and effect seems to be the largest Ideally suited to the Demokritos tandem energy range of MV Needed: terminal gas stripper to produce pure ground state He-like beams – low intensity beams ~1-10nA. Will use electron hemispherical spectrometer with position sensitive detector for high quality statistics ideally suited for working with low intensity beams Spectrometer and collision chamber already in house however need to be connected to a new beam line

1/11/2007 New ZAPS setup: Single stage 0 0 HDA with injection lens and 2-D position sensitive detector F 7+ 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

The end – thank you for listening Contact: Non-statistical results Tanis et al. PRL 92 (2004) Tanis et al. PRL 92 (2004) Zouros et al. PRA 77 (2008) Zouros et al. PRA 77 (2008) Strohschein et al. PRA 77 (2008) Strohschein et al. PRA 77 (2008) Rohrbein et al, PRA 81 (2010) Rohrbein et al, PRA 81 (2010) Production of pure ground state He-like ion beams Benis & Zouros, PRA 65 (2002) Benis & Zouros, PRA 65 (2002) References

Yield corrections due to 4 P J metastability 1.1 MeV/u Important Yield correction

Yield corrections due to 4 P J metastability Important Yield correction 1.1 MeV/u

Yield corrections due to 4 P J metastability 1.1 MeV/u Important Yield correction 1.1 MeV/u