high resolution auger projectile electron spectroscopy of li-like ions produced by electron capture...
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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. ZourosDept. of Physics, University of Crete,
Heraklion, Crete, GREECEAtomic Collisions & Electron Spectrometry Laboratory
&Institute of Nuclear and Particle Physics, Demokritos, Athens
Focus on
CDAMOP Delhi Mar 12, 2015
Non-statistical production of 1s2s2p 4P and 1s2s2p 2P states by
e- capture to the 1s2s 3S state:A persisting puzzle!
Accelerator-based atomic physics topic(ion-atom collisions)
1s2s2p 3-electron spectrum resulting
from e- capture to He-like beame- Analyzer
F6+ (1s2s 3S2p) ion
CDAMOP Delhi Mar 12, 2015
2P±
4P1480 1500 1520 1540
0
2
4
6
8
10
12
14
12 MeV C4+ W=1521eV, F=4 (VL4=-684.45V,VL5=1399.32V)
1s2
p2 2 D
1s(2
s2
p1 P)2 P
+
1s(2
s2
p
3 P)2 P
-
1s2s2p 4P
1s2
s2 2 S
Ne (20mTorr)
No
rma
lize
d e
lectr
on
Yie
lds (
x 1
0-1
1 )
Laboratory Energy (eV)
R = 4P/(2P+ + 2P-)
C4+ (1s2) 75%
C4+ (1s2s 3S) 20% τ1/2 = 20.6 ms
τ1/2 = ∞ - stable
e- Analyzer
CDAMOP Delhi Mar 12, 2015
1s2s2p 3-electron spectrum resulting from e- capture to He-like beam
F6+ (1s2s 3S2p) ion
2P±
4P
Interest in ratio4P/2P
1480 1500 1520 15400
2
4
6
8
10
12
14
12 MeV C4+ W=1521eV, F=4 (VL4=-684.45V,VL5=1399.32V)
1s2
p2 2 D
1s(2
s2
p1 P)2 P
+
1s(2
s2
p
3 P)2 P
-
1s2s2p 4P
1s2
s2 2 S
Ne (20mTorr)
No
rma
lize
d e
lectr
on
Yie
lds (
x 1
0-1
1 )
Laboratory Energy (eV)
R = 4P/(2P+ + 2P-)
He-like beam components:
C4+ (1s2s 1S) 5% τ1/2 = 3 μs
Obtaining pure ground state beam contributions
Foilstripping
Gas stripping
CDAMOP Delhi Mar 12, 2015
Mixed state (1s2, 1s2s 3S) Spectrum
25% metastable
Theory
Obtaining pure ground state beam contributions
Benis et al PRA 2004
Foilstripping
Gas stripping
Gas stripping at lower energiesProduces He-like ions mostly in ground state!
CDAMOP Delhi Mar 12, 2015
Mixed state (1s2, 1s2s 3S) Spectrum
25% metastable
TheoryPractically pure ground state (1s2)
Spectrum< 3% metastable
CDAMOP Delhi Mar 12, 2015
Ratio 4P/2P
1480 1500 1520 15400
2
4
6
8
10
12
14
12 MeV C4+ W=1521eV, F=4 (VL4=-684.45V,VL5=1399.32V)
2D
2P+
2P-
4P
2S
Ne (20mTorr)
Nor
mal
ized
ele
ctro
n Y
ield
s (x
10
-11)
Laboratory Energy (eV)
R = 4P/(2P+ + 2P-)
• Independent of most instrumental parameters (i.e. detector efficiency, number of ions, target pressure, etc.)
• Obey spin statistics• Unexpected value could reveal existence of underlying processes
Spin statistics for 2p capture to pure 1s2s 3S
Sss 321
He-likeInitial States
+ 2p
Sss 121
Ss 121
CDAMOP Delhi Mar 12, 2015
6
4
6
2
Probability
PpSss 23 2)21(
Spin statistics for 2p capture to 1s2s 3S
PpSss 43 2)21(
Sss 321
He-likeInitial States
+ 2p
Sss 121
1s2
CDAMOP Delhi Mar 12, 2015
1480 1500 1520 15400
2
4
6
8
10
12
14
12 MeV C4+ W=1521eV, F=4 (VL4=-684.45V,VL5=1399.32V)
2D
2P+
2P-
4P
2S
Ne (20mTorr)
Norm
alized e
lectr
on Y
ield
s (
x 1
0-1
1 )
Laboratory Energy (eV)
R = 4P/(2P+ + 2P-)
6
4
6
2
Probability
PpSss 23 2)21(
Spin statistics for 2p capture to 1s2s 3S
PpSss 43 2)21(
Li-likeFinal States
Sss 321
He-likeInitial States
+ 2p
Sss 121
1s2
Ppss 4221
1480 1500 1520 15400
2
4
6
8
10
12
14
12 MeV C4+ W=1521eV, F=4 (VL4=-684.45V,VL5=1399.32V)
2D
2P+
2P-
4P
2S
Ne (20mTorr)
Norm
alized e
lectr
on Y
ield
s (
x 1
0-1
1 )
Laboratory Energy (eV)
R = 4P/(2P+ + 2P-)
PPpss 23 )22(14
1
6
4
6
2
Probability
PpSss 23 2)21(
Spin statistics for 2p capture to 1s2s 3S
PpSss 43 2)21(
Li-likeFinal States
PPpss 21 )22(14
3
Spin recouplingSss 321
He-likeInitial States
+ 2p
Sss 121
1s2
Ppss 4221
4P : 2P- : 2P+
12
3
12
1
12
8
Final breakdown 2:1
CDAMOP Delhi Mar 12, 2015
Ratio 4P/2P
1480 1500 1520 15400
2
4
6
8
10
12
14
12 MeV C4+ W=1521eV, F=4 (VL4=-684.45V,VL5=1399.32V)
2D
2P+
2P-
4P
2S
Ne (20mTorr)
Nor
mal
ized
ele
ctro
n Y
ield
s (x
10
-11)
Laboratory Energy (eV)
R = 4P/(2P+ + 2P-)
Expected ratio from spin statisticsAfter subtraction ofGround state “contamination”
4P/2P = 2
Obtaining pure metastable beam contributions
Strohschein et al PRA 2008 CDAMOP Delhi Mar 12, 2015
Obtaining pure metastable beam contributionsPure metastable stateMixed – Norm. Ground state =
In 2008Tanis and companyUsed 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 2D 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
CDAMOP Delhi Mar 12, 2015
So why the bigdiscrepancy!?
Ratio of 4P/2P
First explanation: Pauli exchange interaction?
• An electron with antialigned spin can populate either the 1s, 2s or 2p levels, in the later case giving rise to the 2P+ state
• Cannot form 1s2s2p 4P
CDAMOP Delhi Mar 12, 2015
WMU
1s2s 3S
Pauli exchange interaction
• A target electron with spin aligned to the spin of the 1s projectile:
a) can be captured into the 2p directly to form the 1s2s2p 4P
b) CANNOT be captured into the 1s (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!)
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 4P states
CDAMOP Delhi Mar 12, 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!
nl
Alternative hypothesis: Cascade feeding
OrderCascade feeding 1s2s2p 4P analysis
Quartet Doublet NOT allowed!
Quartet Quartet allowed!
Strong cascade feeding of 1s2s2p 4P !
For a state p:
transitionsdepopulating populating
E1Selection Rules:
CDAMOP Delhi Mar 12, 2015
Cool!
Slow A
uger
Order
Zouros et al, Phys. Rev. A Rapid Comm. 2008
Cascade feeding 1s2s2p 4P analysis
CDAMOP Delhi Mar 12, 2015
Slow A
uger
CDAMOP Delhi Mar 12, 2015
But wait a minute!
Shouldn’t the cascades also feed the 2P states tooThus also enhancing the denominator
of the 4P/2P ratio?
Indeed! But …
OrderCascade feeding 1s2s2p 2P 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 2P ! CDAMOP Delhi Mar 12, 2015
Fast
Aug
er
Order
Zouros et al, Phys. Rev. A Rapid Comm. 2008
Cascade feeding 1s2s2p 2P analysis
CDAMOP Delhi Mar 12, 2015
Fast
Aug
er
This selective Cascade feeding
mechanism accounts
for about 50% of the observed enhancement
Similar results also presented for C4+
So what is the rest due to?Strohschein et al PRA 2008
70%
Röhrbein, Kirchner, Fritzsche PRA 2010
EXCELLENT QUESTION!
CDAMOP Delhi Mar 12, 2015
In progress:• 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
Investigation of the systematics of the 4P/2P ratio in an Isoelectronic sequence study using He-like ions from Li+ , B3+ , C4+ , N5+ , O6+ , F7+ in the 0.1-2 MeV/u
Use different targets such as H2, He, Ne, Ar Ideally suited to the Demokritos tandem
accelerator energy range of 0.8-5 MV.
2013 - APAPES Proposal granted!
New results 2014-2015
APAPES Strohschein 2008
CDAMOP Delhi Mar 12, 2015
Comparison
0
50
100
150
12 MeV C4+
2D
2P+
2P-
4P
2S
Mixed (1s2 + 1s2s 3S) Gaussian fits
C4+ + Ne
12 MeV C4+
220 225 230 235 240 245 2500
2
4
6
8
10
12
No
rma
lize
d Y
ield
s (
arb
.un
its)
Electron Energy (eV)
C4+ + He
Similar energy resolution
New results 2014-2015APAPES
Our new results look very similar – except for 2-3 times larger and wider 4P!???
Comparison
0
50
100
150
200
250
12 MeV C4+
2D
2P+
2P-
4P
2S
Mixed (1s2 + 1s2s 3S) Gaussian fits
C4+ + Ne
12 MeV C4+
220 225 230 235 240 245 2500
5
10
15
20
No
rma
lize
d Y
ield
s (
arb
.un
its)
Electron Energy (eV)
C4+ + He
Strohschein 2008
0.25 0.50 0.75 1.00 1.25 1.50 1.750
3
6
9
spin statistics
C4+ + He WMU (4P/2P)
APAPES (4P/2P)
Incident C4+ Energy (MeV/u)
0
3
6
9 WMU (4P/2P)
APAPES (4P/2P)
4 P/2 P
C4+ + Ne
spin statistics
CDAMOP Delhi Mar 12, 2015
Ratio comparison
NewResults
Give muchLower 4P/2PRatio!
But much closer
To 2!
(after correction for solid angle effect in 4P due to its long life time)
CDAMOP Delhi Mar 12, 2015
Consistency Check ratio
2P+/2P-
Preliminary! However
2P+/2P-Ratio seems
Good For all!
0.25 0.50 0.75 1.00 1.25 1.50 1.750
3
6
9
spin statistics
spin statistics
C4+ + He WMU (4P/2P)
APAPES (4P/2P)
WMU (2P+/2P-)
APAPES (2P+/2P-)
Incident C4+ Energy (MeV/u)
0
3
6
9
spin statistics
spin statistics
2P+
/ 2P-
WMU (4P/2P)
APAPES (4P/2P)
WMU (2P+/2P-)
APAPES (2P+/2P-)
4 P/2 P
C4+ + Ne
CDAMOP Delhi Mar 12, 2015
0
2
4
6
Norm.yields Norm.fit
Ne
12 MeV C4+ W=1521eV,F=4, VL4 =-684.45V,VL5=1399.32V
0
2
4
He4P
2P-2P+ 2D
0
2
4
Nor
mal
ized
ele
ctro
n Y
ield
s (x
10-1
1)
(arb
.uni
ts)
H2
2S
220 225 230 235 240 245 2500
2
4
Auger electron Energy (eV)
ArNew calculations are needed
to evaluate capture and cascade contributions for all measured
collision systems
More New results 2014-2015
0
1
2
3
4
5
6
2P-
Ne (20 mTorr) Fit
18 MeV C4+ W=1966eV, F=4
2P+
Nor
mal
ized
ele
ctro
n Y
ield
s (
10-1
1 )
2S
4P
2D
0
1
2
3
Ne (20 mTorr) Fit
2S
4P
2P-2P+
2D
220 225 230 235 240 245 250
0
1
2
3
4
5
6
2P-
Ar (5 mTorr) Fit
2S
4P
2P+
2D
220 225 230 235 240 245 250
0
1
2
3
2P-
Ar (5 mTorr) Fit
12 MeV C4+ W=1521eV, F=4
Auger Electron Energy (eV)
2S
4P
2P+
2D
New targets Higher Energy – 18 MeV
Zero-degree Auger Projectile spectroscopy setups:1s2s2p 4P yield correction for long-life times
CDAMOP Delhi Mar 12, 2015
WMUAPAPES -12 MeV C4+
10-4
10-3
10-2
10-1
100
101
10-5
10-4
10-3
10-2
10-1
0 50 100 150 200 250 300
10-7
10-6
10-5
10-4
10-3
10-2
0(s
0-z
) (
sr)
= m
ax
J=1/2 =3.7 ns J=3/2 =13.2 ns J=5/2 =117.2 ns
Tem
pora
l Ter
m F
T (
mm
-1)
0(s
0-z
) F
T(z
) (s
r/m
m)
Z (mm)
28.9cm
1.1 MeV/u
F7+
τ1/2 = 0.735 ns
τ3/2 = 7.88 ns
τ5/2 = 16.3 ns
5.8cm
ImportantYield correction
Factor (x 2.5)
1.1 MeV/u
For C4+ 4P correction factors:
7.3, 8.8, 10.2 for 6, 9, 12 MeVStrohschein PRA 2008
1s2s2p 4P metastable solid angle correction factor – WMU – two-stage parallel plate Analyser (2PPA)
CDAMOP Delhi Mar 12, 2015
1.1 MeV/u
F7+
τ1/2 = 0.735 ns
τ3/2 = 7.88 ns
τ5/2 = 16.3 ns
5.8cm
10-4
10-3
10-2
10-1
100
101
10-5
10-4
10-3
10-2
10-1
0 50 100 150 200 250 300
10-7
10-6
10-5
10-4
10-3
10-2
0(s
0-z
) (
sr)
= m
ax
J=1/2 =3.7 ns J=3/2 =13.2 ns J=5/2 =117.2 ns
Tem
pora
l Ter
m F
T (
mm
-1)
0(s
0-z
) F
T(z
) (s
r/m
m)
Z (mm)
CDAMOP Delhi Mar 12, 2015
APAPES
Calculated by SIMION Monte Carlo
12 MeV C4+
1s2s2p 4P metastable solid angle correction factor – APAPES Hemispherical Deflector Analyzer (HDA)
28.9cm
Summary and Conclusion
CDAMOP Delhi Mar 12, 2015
• More measurements still needed for different collision systems to better check systematics (APAPES) • Follow up cascade calculations• Tests of solid angle correction factors to 4P• Can someone please calculate the Pauli Exchange Interaction?
• Controversy still remains: Corrected 4P/2P ratio for C4+ either
too large (WMU) or too small (APAPES)!• New results even more controversial! Still preliminary – need to be checked further
APAPES Main team
• Dept. of Physics, Univ. of Crete, Heraklion
Theo Anastasios Ioannis Angelos Zouros Dimitriou Madesis Laoutaris (Prof & PI) (PostDoc) (PhD student) (MS student) CDAMOP Delhi Mar 12, 2015
APAPES important
participants
CDAMOP Delhi Mar 12, 2015
Manolis Bela Omer Genoveva Jose Benis Sulik Sise Martinez-Lopez Paulo Santos (Prof) (Prof) (Prof) (Prof) (Prof)
Dept of PhysicsUniv of Ioannina
Greece
ATOMKIDebrecenHungary
Univ of IspartaTurkey
Dept Fisica Aplicada Madrid,
Spain
Dept de FisicaUniv Nova de Lisboa
Portugal
CPO simulationsZoom lenses
AtomicStructure
calculations
SpirosDoukas
U. Ioannina
SIMION
Measurements
APAPESSupport
Team
5MV Tandem, Institute of Nuclear and Particle Physics 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
The end thank you for listeningI 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.
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