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...
TRANSCRIPT
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INVESTIGATION OF THE NON-STATISTICAL PRODUCTION RATIO OF 1S2S2P 4P AND
1S2S2P 2P STATES BY e- CAPTURE TO THE 1S2S 3S STATE OF He-LIKE
IONS: A PROGRESS REPORT
XXIV ISIAC Barcelona July 19-21, 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
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ISIAC Barcelona July 19-21, 2015
+
: C4+, F7+, B3+ : H2, He, Ne, Ar, …
Also want to do Li+, N5+, O6+
He-like Ion Beams: Gas targets
0.1 – 2 MeV/u
Production of 1s2s2p 4P and 1s2s2p 2P states by
e- capture to the 1s2s 3S state of He-like ions
@ the 5 MV Tandem of DemokritosAthens, Greece
APAPES project (http://apapes.physics.uoc.gr)
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1s2s2p 3-electron spectrum resulting
from e- capture to He-like beame- Analyzer
F6+ (1s2s 3S2p) ion
ISIAC Barcelona July 19-21, 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-)
Interest in ratio4P/2P
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ISIAC Barcelona July 19-21, 2015
What’s in a Ratio? R=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
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ISIAC Barcelona July 19-21, 2015
Ratio R=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”
R= 4P/2P = 2
2P+/2P- = 3Additional new check:
2P= 2P+ + 2P-
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Obtaining pure metastable beam contributions
Strohschein et al PRA 2008
Spin statistics
Pure metastable state
ISIAC Barcelona July 19-21, 2015
So why the bigdiscrepancy!?
Ratio of 4P/2P
WMU
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First explanation: Pauli exchange interaction?
ISIAC Barcelona July 19-21, 2015
WMU
Alternative hypothesis: Cascade feeding
UoC
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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
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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:
ISIAC Barcelona July 19-21, 2015
Cool!
Slow A
uger
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New plots based on the work ofRöhrbein et at Phys. Rev. A 2010
Cascade feeding 1s2s2p 4P analysis
ISIAC Barcelona July 19-21, 2015
Slow A
ugerOrder
c0
c1c2
10 14 10 12 10 10 10 8 10 6 10 4t s
0.0001
0.0002
0.0003
0.0004
0.0005
N4P t
c0
c1
c2σ4P(t)
t (s)
Strong cascadeFeeding!For t >10-11s
1 MeV/u C4+ + He
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ISIAC Barcelona July 19-21, 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 …
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Order
c0
c1c2
Cascade 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 ! ISIAC Barcelona July 19-21, 2015
Fast
Aug
er
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Order
c0
c1c2
Cascade feeding 1s2s2p 2P analysis
ISIAC Barcelona July 19-21, 2015
Fast
Aug
erNew plots based on the work of
Röhrbein et at Phys. Rev. A 2010
10 14 10 12 10 10 10 8 10 6 10 4t s
0.00005
0.00010
0.00015
N2P tσ2P(t)
t (s)
c0
c1
c2
No cascadeFeeding!
State depletedfor t >10-12s
1 MeV/u C4+ + He
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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!
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ISIAC Barcelona July 19-21, 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!
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New results 2014-2015
APAPES Strohschein 2008
ISIAC Barcelona July 19-21, 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
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ISIAC Barcelona July 19-21, 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
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Zero-degree Auger Projectile spectroscopy setups:1s2s2p 4P yield correction for long-life times
ISIAC Barcelona July 19-21, 2015
WMU
1 MeV/u
C4+
τ1/2 = 2.8 ns
τ3/2 = 7.3 ns
τ5/2 = 120 ns
5.8cm
APAPES -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
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Zero-degree Auger Projectile spectroscopy setups:1s2s2p 4P yield correction for long-life times
ISIAC Barcelona July 19-21, 2015
WMU
1 MeV/u
C4+
τ1/2 = 2.8 ns
τ3/2 = 7.3 ns
τ5/2 = 120 ns
5.8cm
For C4+1s2s2p 4P correction factors:
7.3, 8.8, 10.2 for 6, 9, 12 MeVStrohschein PRA 2008
c0
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1s2s2p 4P metastable solid angle correction factor – WMU – two-stage parallel plate Analyser (2PPA)
ISIAC Barcelona July 19-21, 2015
0.1 1 10 100 1000z m m 0.005
0.010
0.015
0.020
0.025
0.030
0.035
Norm dN dz J 1 2
2PPA entry
Lost e-Detected e-
Comparison for c0 and c2
z (mm) – distance from target z = Vp t
dN/dz
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1s2s2p 4P metastable solid angle correction factor – WMU – two-stage parallel plate Analyser (2PPA)
ISIAC Barcelona July 19-21, 2015
No cascadecorrection
New point!With cascadesc2 correction
Röhrbein, Kirchner, Fritzsche PRA 2010
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Summary and Conclusions
ISIAC Barcelona July 19-21, 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?
• c2 Cascades included in the solid angle correction factor Now Corrected 4P/2P ratio for C4+
in much better agreement with theory!
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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
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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) ISIAC Barcelona July 19-21, 2015
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APAPES important
participants
ISIAC Barcelona July 19-21, 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
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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
ISIAC Barcelona July 19-21, 2015
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The end thank you for listening
More info? Please Contact me: [email protected]
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 377289.
Recent publication: Doukas et al. RSI 84 (2015) 043111