manolis benis formation mechanisms of the 1s2s2p 4 p j metastable state in 12 mev c 4+ (1s 2 1 s,...

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


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


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


Populating the 1s2l2l' states

NTE

V

V

RTE

Target Projectile

V

T (or C)


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


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


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


Strohschein et al PRA 2008


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


Radiative Cascade feeding (?)

Significant capture to higher n=3-7 indicated by CDW calculations

nl

Zouros et al PRA2008


Radiative Cascade feeding (?)

TJM Zouros, B. Sulik, L. Gulyas, K.Tokesi , PRA 77, 050701R (2008)


Current Status

Strohschein et al PRA 2008 (50%)

Röhrbein et al PRA 2010 (70%)


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


The effective solid correction factor

Doukas et al RSI (accepted)


SIMION simulations

Doukas et al RSI (accepted)


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%


d2/

dd

(10

-20 c

m2/ e

V s

r)

Benis et al PRA 2004

4MeV

B3+

+H

2


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


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)


C4+ + He

Results look very similar – except for 2-3 times larger 4P (higher efficiency of our spectrograph)


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


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


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.

manolis benis formation mechanisms of the 1s2s2p 4 p j metastable state in 12 mev c 4+ (1s 2 1 s,...

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