Transcript Ion-atom Collisions

Formation mechanisms of the 1s2s2p 4PJ metastable state in
12 MeV C4+ (1s2 1S, 1s2s 3S) collisions with H2, He, Ne and Ar
Manolis Benis
Department of Physics, University of Ioannina
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
Atomic
Energy
levels
continuum
Ea - Auger energy
e-e interaction M
L
Ex
K
capture
K
ionization
K-M
excitation
Ion-atom collision
e-
e-
vt
Zp
Vp
b
Projectile
Ion
Charge q+
Zt
Target
Atom
PIPAMON workshop, Debrecen, March 24-26, 2015
M-K
radiative
transition
K
KLM
Auger
transition
Atomic Structure: q, Zp, Zt , Ex, Ea…
Collision Dynamics: b, Vp , vt …
Cross section:  (Vp , q, Z p , b, vt , Zt , Ea , Ex ,...)
HCI: Few-electrons - simpler environment
for testing theories
Projectile spectroscopy: Control # of
electrons on ion by selecting its charge
Special interest: Two-electron processes, ecorrelations and deviations from the IPM
Populating the 1s2l2l' states
T (or C)
V
RTE
V
NTE
V
Target
Projectile
PIPAMON workshop, Debrecen, March 24-26, 2015
Spin statistics for 2p capture to 1s2s 3S
Spin recoupling
Probability
4
(1s(2s 2 p)3 P) P
6
4
(1s 2s S )2 p P
6
3
4
4
3
1s 2s S + 2p
1
(1s(2s 2 p) P) P
4
3
2
(1s 2s S )2 p P
6
3
Final
breakdown
4P
2
: 2P- : 2P+
8
1
3


12 12 12
PIPAMON workshop, Debrecen, March 24-26, 2015
2
4
3
(1s(2s 2 p) P) P
4
P
R 2
2
2
P  P
3
2
P
R 2 3
P
2
Literature Overview
7
Lee (1991)
Tanis (2004)
6
4
2
2
Ratio - R = e( P)/[e( P+) + e( P--)]
Data:
5
4
3
2
1
7+
2
3
F (1s /1s2s S) + He
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Projectile Energy (MeV/u)
2
Ratio - R = e( P)/[e( P+) + e( P--)]
7
5
4
2
Spin statistics
6
4
3
2
1.875
1
7+
2
3
F (1s /1s2s S) + H2
0
Strohschein et al PRA 2008
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Projectile Energy (MeV/u)
Zouros et al PRA 2008
PIPAMON workshop, Debrecen, March 24-26, 2015
2.0
Mixed state (1s2 1S, 1s2s 3S ) beams
8
22
6
4
1
22
2
2
1s2p D
+ H2
2
0
14
12
f S < 3%
3
10
2
Practically ground state (1s2)
spectrum. < 3% metastable
Ion Beam obtained by gas stripping
at lower energies
d /dd (10
“Subtract” spectra to obtain pure metastable
beam 1s2s 3S spectrum!
-20
2
Mixed state
1s2s
spectrum
25% metastable
Ion Beam obtained by foil stripping
1s2s S
3S)
cm / eV sr)
10
(1s2,
3
3
1s(2s2p P) P
f S = 25%
4
12
1s2s2p P
14
1s(2s2p P) P
3+
4 MeV B
8
6
4
2
0
Use both measurements to obtain the fractions
Benis et al PRA 2004
PIPAMON workshop, Debrecen, March 24-26, 2015
150 152 154 156 158 160 162 164 166 168 170
Electron Energy (eV)
Mixed state (1s2 1S, 1s2s 3S ) beams
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:
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
New idea: So instead it interacts with the 1s (or
2s) via a Pauli Exchange Interaction with one etransferred to the 2p forming additional 4P
states
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!)
PIPAMON workshop, Debrecen, March 24-26, 2015
Radiative Cascade feeding (?)
nl
Zouros et al PRA2008
Significant capture to higher n=3-7
indicated by CDW calculations
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
Röhrbein et al PRA 2010 (70%)
Strohschein et al PRA 2008 (50%)
PIPAMON workshop, Debrecen, March 24-26, 2015
Ion-atom Collisions
Ne
d

d N I  n  l  0  T 
Ne
1
 d 



 d  PROMPT N I  n  l  T  0
Ne
1
 d 



 d  META N I  n  l  T  eff
PIPAMON workshop, Debrecen, March 24-26, 2015
0
 d 
 d 





 d  META  d  PROMPT eff
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
22
1s2s S
8
6
4
1
22
2
2
1s2p D
+ H2
2
0
14
12
f S < 3%
3
10
2
d /dd (10
4MeV B3+ +H2
-20
2
cm / eV sr)
10
3
3
1s(2s2p P) P
f S = 25%
4
12
1s2s2p P
14
1s(2s2p P) P
3+
4 MeV B
8
6
4
2
0
150 152 154 156 158 160 162 164 166 168 170
Electron Energy (eV)
Benis et al PRA 2004
PIPAMON workshop, Debrecen, March 24-26, 2015
Current and future prospects


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
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
PIPAMON workshop, Debrecen, March 24-26, 2015
Ongoing Research
APAPES
Strohschein 2008
150
2
3
Mixed (1s + 1s2s S)
Gaussian fits
4
P
12 MeV C
2
100
P+
Normalized Yields (arb.units)
C
2
P-
2
S
50
4+
4+
+ Ne
2
D
0
12 MeV C
12
C
10
4+
4+
+ He
8
6
4
2
0
220
225
230
235
240
245
250
Electron Energy (eV)
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 targets
Higher Energy – 18 MeV
6
6
4
5
W=1521eV,F=4,
VL4 =-684.45V,
VL5=1399.32V
Ne
2
0
-11
4
2
4
P
2
S
He
2
P-
2
P+
P
4+
18 MeV C
W=1521eV, F=4
Ne (20 mTorr)
Fit
4
2
2
D
3
4
2
2
2
2
P
2
D
2
2
S
0
6
P-
5
Ar (5 mTorr)
Fit
4
P
4
P
3
2
P+
2
S
1
P-
2
D
0
2
D
2
1
220
H2
2
Ar (5 mTorr)
Fit
4
4
2
Norm.yields
Norm.fit
P+
0
3
2
0
W=1966eV, F=4
1
2
P-
S
1
P+
4+
Ne (20 mTorr)
Fit
-11
Normalized electron Yields (  10 )
12 MeV C
4+
4
Normalized electron Yields (x10 ) (arb.units)
3
12 MeV C
2
2
S
2
P-
P+
2
D
0
225
230
235
240
245
250
220
225
230
235
240
245
250
Auger Electron Energy (eV)
0
4
Ar
2
0
220
225
230
235
240
245
Auger electron Energy (eV)
PIPAMON workshop, Debrecen, March 24-26, 2015
250
New calculations are needed
to evaluate capture and cascade
contributions for all measured
collision systems
The team
5MV Tandem
NCSRT Demokritos
Prof. Theo Zouros Prof. Manolis Benis
Univ. of Crete
Univ. of Ioannina
Prof. Bela Sulik
ATOMKI
Dr S. Harissopulos
(Director)
Dr T. Lagogiannis
Prof. Omer Sise
Univ. of Isparta
Dr. M. Axiotis
M. Andrianis
Dr. A. Dimitriou (Post doc)
I. Madesis (PhD)
A. Laoutaris (MSc)
PIPAMON workshop, Debrecen, March 24-26, 2015
S. Doukas (MSc)
Univ. of Ioannina
Thank you for your attendance
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.
PIPAMON workshop, Debrecen, March 24-26, 2015