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...

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

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)

http://apapes.physics.uoc.gr/

http://apapes.physics.uoc.gr/

1s2s2p 3-electron spectrum resulting

from e- capture to He-like beame- Analyzer

F6+ (1s2s 3S2p) ion


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


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)


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


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)


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-

Obtaining pure metastable beam contributions

Strohschein et al PRA 2008

Spin statistics

Pure metastable state


So why the bigdiscrepancy!?

Ratio of 4P/2P

WMU

First explanation: Pauli exchange interaction?


WMU

Alternative hypothesis: Cascade feeding

UoC

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:


Cool!

Slow A

uger

New plots based on the work ofRöhrbein et at Phys. Rev. A 2010

Cascade feeding 1s2s2p 4P analysis


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


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 …

Order

c0

c1c2


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

Order

c0

c1c2



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

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!


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


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


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


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

Zero-degree Auger Projectile spectroscopy setups:1s2s2p 4P yield correction for long-life times


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

1s2s2p 4P metastable solid angle correction factor – WMU – two-stage parallel plate Analyser (2PPA)


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

1s2s2p 4P metastable solid angle correction factor – WMU – two-stage parallel plate Analyser (2PPA)


No cascadecorrection

New point!With cascadesc2 correction

Röhrbein, Kirchner, Fritzsche PRA 2010

Summary and Conclusions


• 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!


Tom Kirchner York University

Toronto, Ontario, Canada

In April 2015 joined the APAPES collaboration

THEORY – Capture calculations and Analytic Cascade formulation

Curtis, AJP 1968

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

APAPES important

participants


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


The end thank you for listening

More info? Please Contact me: [email protected]


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

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...

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