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69th NUPECC meeting October 8, 2010
1
Electron transferElectron transfer into into metastable metastable HeHe-like ions: -like ions:
Investigation of Investigation of non-statistical non-statistical population mechanisms population mechanisms
Theo J.M. ZourosTheo J.M. ZourosDept. of Physics, University of Crete Dept. of Physics, University of Crete
Heraklion, Crete, GREECEHeraklion, Crete, GREECE
A proposal for A proposal for atomic collisionatomic collision experiments experiments at the Demokritos TANDEMat the Demokritos TANDEM
3-electron spectrum 3-electron spectrum from collisions of He-like beamfrom collisions of He-like beam
1.1 MeV/u1.1 MeV/u
F F 7+7+ (1s (1s22) 75%) 75%
F F 7+7+ (1s2s (1s2s 11S) <1%S) <1%F F 7+7+ (1s2s (1s2s 33S) 24%S) 24% ττ1/21/2 = = 277 277 μμss
ττ1/21/2 = 0.198 = 0.198 μμss
ττ1/21/2 = = stablestable
3-electron spectrum 3-electron spectrum from collisions of He-like beamfrom collisions of He-like beam
1.1 MeV/u1.1 MeV/u
F F 7+7+ (1s (1s22) 75%) 75%
F F 7+7+ (1s2s (1s2s 11S) <1%S) <1%F F 7+7+ (1s2s (1s2s 33S) 24%S) 24% ττ1/21/2 = = 277 277 μμss
ττ1/21/2 = 0.198 = 0.198 μμss
ττ1/21/2 = = stablestable
Spin statistics for 2p capture to Spin statistics for 2p capture to purepure 1s2s 1s2s 33S S
Sss 321
HeHe-like-likeInitial StatesInitial States
+ 2p+ 2p
Sss 121
Ss 121
<1 %<1 %
6
4
6
2
ProbabilityProbability
PpSss 23 2)21(
Spin statistics for 2p capture to 1s2s Spin statistics for 2p capture to 1s2s 33S S
PpSss 43 2)21(
Sss 321
HeHe-like-likeInitial StatesInitial States
+ 2p+ 2p
Sss 121
1s1s22
6
4
6
2
ProbabilityProbability
PpSss 23 2)21(
Spin statistics for 2p capture to 1s2s Spin statistics for 2p capture to 1s2s 33S S
PpSss 43 2)21(
LiLi-like-likeFinal StatesFinal States
Sss 321
HeHe-like-likeInitial StatesInitial States
+ 2p+ 2p
Sss 121
1s1s22
Ppss 4221
PPpss 23 )22(14
1
6
4
6
2
ProbabilityProbability
PpSss 23 2)21(
Spin statistics for 2p capture to 1s2s Spin statistics for 2p capture to 1s2s 33S S
PpSss 43 2)21(
LiLi-like-likeFinal StatesFinal States
PPpss 21 )22(14
3
Spin recouplingSpin recouplingSss 321
HeHe-like-likeInitial StatesInitial States
+ 2p+ 2p
Sss 121
1s1s22
Ppss 4221
44P : P : 22PP__ : : 22PP++
12
3
12
1
12
8Final Final
breakdownbreakdown 2:12:1
Obtaining Obtaining purepure metastable beam contributions metastable beam contributions
Strohschein et al PRA 2008Strohschein et al PRA 2008
Obtaining Obtaining purepure metastable beam contributions metastable beam contributions
Strohschein et al PRA 2008Strohschein et al PRA 2008
Pure metastablePure metastable = Mixed - Ground= Mixed - Ground
Obtaining pure metastable beam contributionsObtaining pure metastable beam contributions
Strohschein et al PRA 2008Strohschein et al PRA 2008
Spin statisticsSpin statistics
So why the bigSo why the bigdiscrepancy???discrepancy???
Pauli exchange interactionPauli exchange interaction
• An electron with An electron with antialignedantialigned spin spin can populate either the 1s, 2s or can populate either the 1s, 2s or 2p2p levels, in the later case giving levels, in the later case giving rise to the rise to the 22PP++ state state
Pauli exchange interactionPauli exchange interaction
• An electron with a spin An electron with a spin alignedaligned with the spin of the 1s projectile:with the spin of the 1s projectile: a) can be captured into the a) can be captured into the 2p2p directly to form the directly to form the 44PP state state
b) b) cannotcannot be captured into the 1s be captured into the 1s (or 2s) due to (or 2s) due to Pauli exclusion. Pauli exclusion. So instead it interacts with the 1sSo instead it interacts with the 1s (or 2s) via a(or 2s) via a Pauli Exchange InteractionPauli Exchange Interaction so that one of them is transferred toso that one of them is transferred to the the 2p2p forming additional forming additional 44PP states states
Tanis et al Tanis et al PRL2004PRL2004
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
OrderOrderCascade feeding 1s2s2p Cascade feeding 1s2s2p 44P analysisP analysis
Quartet Quartet Doublet Doublet NOTNOT allowed!allowed!
Quartet Quartet Quartet Quartet allowed!allowed!
Strong cascade feeding Strong cascade feeding of 1s2s2p of 1s2s2p 44PP
OrderOrder
Zouros et al, Zouros et al, Phys. Rev. A Rapid Comm. 2008Phys. Rev. A Rapid Comm. 2008
Cascade feeding 1s2s2p Cascade feeding 1s2s2p 44P analysisP analysis
OrderOrderCascade feeding 1s2s2p Cascade feeding 1s2s2p 22P analysisP analysis
All transitions All transitions allowed!allowed!
However However AugerAuger transitions transitions much stronger!much stronger!
They They rapidly depleterapidly deplete higher lying levels!higher lying levels!
NO effective NO effective cascade feeding!cascade feeding!
OrderOrder
Zouros et al, Zouros et al, Phys. Rev. A Rapid Comm. 2008Phys. Rev. A Rapid Comm. 2008
Cascade feeding 1s2s2p Cascade feeding 1s2s2p 22P analysisP analysis
Cascade feeding Cascade feeding accounts accounts
for about 50% for about 50% of the observed of the observed enhancementenhancement
Final verdictFinal verdict
So what is the rest due to?So what is the rest due to?
Proposal• Isoelectronic sequence study using He-like ions from
Li+ to F7+ in the 0.1-0.5 MeV/u where capture is strongest and effect seems to be the largest
Proposal• Isoelectronic sequence study using He-like ions from
Li+ to F7+ in the 0.1-0.5 MeV/u where capture is strongest and effect seems to be the largest
• Ideally suited to the Demokritos tandem energy range of 0.8-4 MV.
Proposal• Isoelectronic sequence study using He-like ions from
Li+ to F7+ in the 0.1-0.5 MeV/u where capture is strongest and effect seems to be the largest.
• Ideally suited to the Demokritos tandem energy range of 0.8-4 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 F7+ in the 0.1-0.5 MeV/u where capture is strongest and effect seems to be the largest.
• Ideally suited to the Demokritos tandem energy range of 0.8-4 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 F7+ in the 0.1-0.5 MeV/u where capture is strongest and effect seems to be the largest
• Ideally suited to the Demokritos tandem energy range of 0.8-4 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 00 HDA with injection lens and 2-D position sensitive detector
5104.14
%,20%,1.0
acceptE
E
E
E
Gas in Pressure Gauge
Gas Cell
PSDX-PositionY- Position
Timing
4-element lens
Faraday Cup
Inner hemisphere
electrons
Outerhemisphere
F7+
Target gas nt ~1012 #/cm3Differential
Pumpingports
Focusing and retardation
Chamber pressure~10-7 Torr
Overall efficiency gain ~ 20-50High Transmission ~ 90%
Paracentric entry
The end – thank you for listeningThe end – thank you for listening
ContactContact: [email protected]: [email protected]
Non-statisticalNon-statistical results results• Tanis et al.Tanis et al. PRL 92 (2004) 133201 PRL 92 (2004) 133201• Zouros et al.Zouros et al. PRA 77 (2008) 050701 PRA 77 (2008) 050701• Strohschein et al.Strohschein et al. PRA 77 (2008) 022706 PRA 77 (2008) 022706• Rohrbein et alRohrbein et al, PRA 81 (2010) 042701, PRA 81 (2010) 042701
Production of Production of purepure ground state He-likeground state He-like ion beams ion beams• Benis & ZourosBenis & Zouros, , PRA 65 (2002) 064701PRA 65 (2002) 064701
ReferencesReferences
Yield correctionsYield corrections due to due to 44PPJJ metastability metastability
1.1 MeV/u1.1 MeV/u
ImportantImportantYield correctionYield correction
Yield correctionsYield corrections due to due to 44PPJJ metastability metastability
ImportantImportantYield correctionYield correction
1.1 MeV/u1.1 MeV/u
Yield correctionsYield corrections due to due to 44PPJJ metastability metastability
1.1 MeV/u1.1 MeV/u
ImportantImportantYield correctionYield correction
1.1 MeV/u1.1 MeV/u