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Manolis Benis
Formation mechanisms of the 1s2s2p 4PJ metastable state in 12 MeV C4+ (1s2 1S, 1s2s 3S) collisions with H2, He, Ne and Ar
Department of Physics, University of Ioannina
PIPAMON workshop, Debrecen, March 24-26, 2015
PIPAMON workshop, Debrecen, March 24-26, 2015
OUTLINE
Ion-atom collisions
Population of the 1s2l2l' states
Literature Overview
Pauli exchange interaction
Radiative cascade feeding
Miscellaneous on mixed state beams and metastable states
Auger decay detection
Results from older measurements
New data from new measurements
Ongoing research at Democritus Infrastructure
PIPAMON workshop, Debrecen, March 24-26, 2015
Ion-atom Collisions
continuum
K
LM
Kcapture
K-M excitation
Ea - Auger energy
KLM Augertransition
e-e interaction
AtomicEnergylevels
Kionization
Atomic Structure: q, Zp, Zt , Ex, Ea…Collision Dynamics: b, Vp , vt …Cross section: HCI: Few-electrons - simpler environment for testing theoriesProjectile spectroscopy: Control # of electrons on ion by selecting its chargeSpecial interest: Two-electron processes, e- correlations and deviations from the IPM
,...),,,v,,,,( xEEZbZqV attpp
M-K radiativetransition
Ex
VpZp
Zt
b
e- e-
Ion-atom collision
vt
ProjectileIonCharge q+ Target
Atom
T+NTE
PIPAMON workshop, Debrecen, March 24-26, 2015
Populating the 1s2l2l' states
NTE
V
V
RTE
Target Projectile
V
T (or C)
PIPAMON workshop, Debrecen, March 24-26, 2015
Spin statistics for 2p capture to 1s2s 3S
Sss 321 + 2p
4P : 2P- : 2P+
12
3
12
1
12
8
Final breakdown
Probability
6
4PpSss 43 2)21(
6
2PpSss 23 2)21(
Spin recoupling
6
4PPpss 43 ))22(1(
PPpss 23 ))22(1(
PPpss 23 ))22(1(
4
1
4
3
222
4
PP
PR 3
2
2
P
PR
PIPAMON workshop, Debrecen, March 24-26, 2015
Literature Overview
Spin statistics
Strohschein et al PRA 2008
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00
1
2
3
4
5
6
7
F7+(1s2/1s2s 3S) + He
Data: Lee (1991) Tanis (2004)
Rat
io -
R =
e(
4 P)/
[e(
2 P+)
+
e(2 P
--)]
Projectile Energy (MeV/u)
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00
1
2
3
4
5
6
7
1.875
Rat
io -
R =
e(4 P
)/[
e(2P
+)
+
e(2 P
--)]
F7+(1s2/1s2s 3S) + H2
Projectile Energy (MeV/u)
Zouros et al PRA 2008
PIPAMON workshop, Debrecen, March 24-26, 2015
Mixed state (1s2 1S, 1s2s 3S ) beams
0
2
4
6
8
10
12
14
1s2s
2 2S
1s2s
2p 4P
1s(2
s2p
3P
) 2P
1s(2
s2p
1P
) 2P
1s2p
2 2Df3S
= 25%
4 MeV B3+ + H2
150 152 154 156 158 160 162 164 166 168 170
0
2
4
6
8
10
12
14
f3S < 3%
Electron Energy (eV)
d2/
dd
(10
-20 c
m2/ e
V s
r)
Use both measurements to obtain the fractions Benis et al PRA 2004
Practically ground state (1s2) spectrum. < 3% metastable
Ion Beam obtained by gas stripping at lower energies
Mixed state (1s2, 1s2s 3S) spectrum25% metastable
Ion Beam obtained by foil stripping
“Subtract” spectra to obtain pure metastable beam 1s2s 3S spectrum!
Mixed state (1s2 1S, 1s2s 3S ) beams
PIPAMON workshop, Debrecen, March 24-26, 2015
Strohschein et al PRA 2008
PIPAMON workshop, Debrecen, March 24-26, 2015
Pauli exchange interaction (?)
A target electron with spin aligned to the spin of the 1s projectile:
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) via a Pauli Exchange Interaction with one e- transferred to the 2p forming additional 4P states
a) can be captured into the 2p directly to form the 1s2s2p 4P
PIPAMON workshop, Debrecen, March 24-26, 2015
Radiative Cascade feeding (?)
Significant capture to higher n=3-7 indicated by CDW calculations
nl
Zouros et al PRA2008
PIPAMON workshop, Debrecen, March 24-26, 2015
Radiative Cascade feeding (?)
TJM Zouros, B. Sulik, L. Gulyas, K.Tokesi , PRA 77, 050701R (2008)
PIPAMON workshop, Debrecen, March 24-26, 2015
Current Status
Strohschein et al PRA 2008 (50%)
Röhrbein et al PRA 2010 (70%)
PIPAMON workshop, Debrecen, March 24-26, 2015
Ion-atom Collisions
0
1
TlnN
N
d
d
I
e
PROMPT
effI
e
META TlnN
N
d
d
1
TlnN
N
d
d
I
e
0
effPROMPTMETA d
d
d
d
0
PIPAMON workshop, Debrecen, March 24-26, 2015
The effective solid correction factor
Doukas et al RSI (accepted)
PIPAMON workshop, Debrecen, March 24-26, 2015
SIMION simulations
Doukas et al RSI (accepted)
PIPAMON workshop, Debrecen, March 24-26, 2015
Revisit of older data
0
2
4
6
8
10
12
14
1s2s
2 2S
1s2s
2p 4P
1s(2
s2p
3P
) 2P
1s(2
s2p
1P
) 2P
1s2p
2 2Df3S
= 25%
4 MeV B3+ + H2
150 152 154 156 158 160 162 164 166 168 170
0
2
4
6
8
10
12
14
f3S < 3%
Electron Energy (eV)
d2/
dd
(10
-20 c
m2/ e
V s
r)
Benis et al PRA 2004
4MeV
B3+
+H
2
PIPAMON workshop, Debrecen, March 24-26, 2015
Current and future prospects
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
PIPAMON workshop, Debrecen, March 24-26, 2015
Ongoing Research
Strohschein 2008APAPES
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
Norm
aliz
ed Y
ield
s (
arb
.units)
Electron Energy (eV)
C4+ + He
Results look very similar – except for 2-3 times larger 4P (higher efficiency of our spectrograph)
PIPAMON workshop, Debrecen, March 24-26, 2015
Ongoing Research
New calculations are needed to evaluate capture and cascade contributions for all measured collision systems
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
Norm
aliz
ed e
lect
ron Y
ield
s (x
10
-11 )
(arb
.units
)
H2
2S
220 225 230 235 240 245 2500
2
4
Auger electron Energy (eV)
Ar
New targets
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
Higher Energy – 18 MeV
PIPAMON workshop, Debrecen, March 24-26, 2015
The team
5MV TandemNCSRT Demokritos
Dr S. Harissopulos (Director)
M. Andrianis
Dr T. Lagogiannis
Dr. M. Axiotis
Dr. A. Dimitriou (Post doc)I. Madesis (PhD)A. Laoutaris (MSc)
Prof. Theo ZourosUniv. of Crete
S. Doukas (MSc)Univ. of Ioannina
Prof. Bela Sulik ATOMKI
Prof. Omer SiseUniv. of Isparta
Prof. Manolis BenisUniv. of Ioannina
Thank you for your attendance
PIPAMON workshop, Debrecen, March 24-26, 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.