Experimental cross sections Experimental cross sections

for electron-impact ionization for electron-impact ionization

and and

electron-ion recombination electron-ion recombination

Research Coordination Meeting, IAEA CRP, Vienna, 26-28 September 2007

Alfred MüllerAlfred MüllerInstitut für Atom- und MolekülphysikInstitut für Atom- und Molekülphysik

JU STUS-LIEBIG - U N IVER SITÄT G IESSEN

I M PA

Experimental work within the CRP Experimental work within the CRP was performed bywas performed by

Stefan SchippersEike SchmidtAlexander Borovik jr.Dietrich BernhardtMohammad Gharaibeh(visting from Irbid, Jordan)Carsten Brandau (now GSI)Sebastian Böhm (now Stockholm)

A.M.

IAMP, Giessen

A. Wolf, M. Grieser, J. Hoffmann, A. S.

Jaroshevich, C. Krantz, D. A. Orlov, R. Repnow, F. Sprenger

MPI-K, Heidelberg

D. W. Savin, M. Lestinsky, D. Lukić, M. Schnell

Columbia University, Astronomy & Astrophysics, New York

OutlineOutline

1. Overview

2. Results on electron-impact ionization of ions Xeq+ , q=1,2,…,15

3. Results on electron-ion recombinationFe13+, Fe14+, Si3+

cross sections for electron-impact single and multiple ionization of ionsespeciallyXeq+ ions q=1,2,…,15and possibly also for Snq+ ions q=1,2,…

rate coefficients for radiative and dielectronic recombination of ions especially Fe8+, Fe13+, Fe14+, Fe16+

Giessen work planned for the present CRPGiessen work planned for the present CRP

Versatile apparatus for studying atomic collisions(additional beamlines not shown)

Electron-ion Electron-ion crossed-beams crossed-beams setup at IAMPsetup at IAMP

Electron-ion beam crossing regionElectron-ion beam crossing region

Xenon ions produced by ECR sourceXenon ions produced by ECR source 2003

Measurement of absolute cross sectionsMeasurement of absolute cross sections

Requirement for the measurement of cross sections:

Beam density distributions → beam overlap → formfactor

Electron-ion beam crossing regionElectron-ion beam crossing region

Measurement of cross sectionsMeasurement of cross sectionsabsolute high precision

Test experiment with LiTest experiment with Li++ (1s (1s22) ions) ions

100 1000

0

1

2

3

4

5

Giessen absolute data, Giessen energy scan

A. Borovik jr., S. Schippers, K. Huber, and A. Müller

Pindzola M.S. et al. Phys. Rev. A 61 (2000) 052712 time-dependent close coupling

Ioni

zatio

n cr

oss

sect

ion

(10-1

8 cm

2 )

Electron energy ( eV )

Ground-state ionizationthreshold at 75.64 eV

10% uncertainty

Ion production: LiIon production: Li++ (1s (1s22) and Li) and Li++ (1s2s) ions (1s2s) ions

0 5 10 15 20 25 30

0

500

1000

1500

2000

2500

1S

Ion

yiel

d (

num

ber

of c

ount

s )

Electron energy ( eV )

3S

Li2+ from Li+ by electron impact

ring magnets

extraction elektrodeplasma chamber

water cooling

hexapole

Electron cyclotron resonance (ECR) ion source

Li, LiF

Depending on source operation there may be metastable ions in the primary ion beam

Li 2+ ion yieldmetallic Li evaporated

threshold at 16.6 eV

Effects of metastable ions on cross sectionsEffects of metastable ions on cross sections

20 1000

2

4

6

8

absolute data, Borovik et al. scan data, Borovik et al. superposititon of theoretical

cross sections for ionization from ground state (88%) and

3S metastable state (12%)

C

ross

sec

tion

( 10-1

8 cm

2 )

Electron energy ( eV )500

Unknown fractions of Unknown fractions of metastable ions in parent ion beamsmetastable ions in parent ion beams

In some cases the metastable content of the primary ion beam can be controlled

More often, when several metastable states contribute, it is difficult to assess their contents in the parent ion beam

A possible way out: store parent ions in a storage ring for sufficiently long times prior to the measurement and let excited states decay

$ $

Measurements on single ionization of XeMeasurements on single ionization of Xe6+6+

60 80 100 200 400 600 80010000

10

20

30

40

50 5s ionization threshold

D.C. Gregory, D.H. Crandall, Phys. Rev. A 27, 2338 (1983)

Cro

ss s

ectio

n ( M

b )

Electron energy ( eV )

Xe6+ + e Xe7+ + 2e

Measurements on single ionization of XeMeasurements on single ionization of Xe6+6+

60 80 100 200 400 600 80010000

10

20

30

40

50

B sig sigmacorr

5s ionization threshold

A. Borovik jr., M. Gharaibeh, S. Schippers, A. Müller, Giessen 2007 D.C. Gregory, D.H. Crandall, Phys. Rev. A 27, 2338 (1983)

Cro

ss s

ectio

n ( M

b )

Electron energy ( eV )

Xe6+ + e Xe7+ + 2e

Metastable XeMetastable Xe6+ 6+ states in the parent ion beam states in the parent ion beam

60 80 100 120 140 160 1800

10

20

30

40

50

5s5p 3P metastableionization thresholds

5s2 ionization threshold

A. Borovik jr., M. Gharaibeh, S. Schippers, and A. Müller Giessen 2007

absolute cross sections energy scan measurement

D.C. Gregory, D.H. Crandall, Phys. Rev. A 27, 2338 (1983)

Cro

ss s

ectio

n ( M

b )

Electron energy ( eV )

Xe6+

„Cold“ Penning ion source and „hot“ ECR ion source

Steps and resonance peaks in single ionization Steps and resonance peaks in single ionization

Griffin et al, 1983

80 100 120 140 160 1800

10

20

30

40

50

5s 5p

5f

6p

5d

Experiment

total single ionization A. Borovik jr. et al. 2007

Distorted Wave Theory

direct ionization Griffin et al. 1983

direct ionization + + excitation-autoionization Griffin et al. 1983

C

ross

sec

tion

( Mb

)

Electron energy ( eV )

Xe6+

4f

resonant and direct4d excitations

Single ionization using beams from ECR sources Single ionization using beams from ECR sources

200 400 600 800 10000

2

4

6

8

10

12

14

620 640 660 680 7009.4

9.6

9.8

10.0

10.2

10.4

4d ionization threshold

absolute data energy scan data Bannister et al.

Xe8+ + e Xe9+ + 2e

Cro

ss s

ectio

n ( M

b )

Electron Energy ( eV )

Electron-impact ionization of XeElectron-impact ionization of Xe10+10+ ions ions

0 100 200 300 400 500 600 700 8000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

580 600 620 640 660 680 700

5.1

5.2

5.3

5.4

5.5

5.6

120 140 160 180 200 220 2400.0

0.1

0.2

0.3

0.4

absolute data energy scan data

Cros

s sec

tion 10

11 (

10-1

8 cm2 )

Electron energy ( eV )

Xenon ions produced by ECR sourceXenon ions produced by ECR source 2007

1350 1400 1450 1500 1550 1600 1650 1700 17500

5

10

15

20

25

Ion

Cur

rent

( n

A)

Magnetic Field ( G )

Xe16+

Xe15+ Xe14+

Xe13+

Xe17+

Xe18+

Xe19+

Xe20+

Xe21+

N2+

C2+

O2+

Xenon ions produced by ECR sourceXenon ions produced by ECR source 2007

3600 3800 4000 42000

1

2

3

4

5

N3+

O3+

Ion

Cur

rent

( nA

)

Magnetic Field ( arbitrary units )

Xe21+

Xe22+

Xe23+

Xe24+

Xe25+Xe26+Xe27+

C2+

3750 3800 3850 3900 39500.000

0.005

0.010

0.015

0.020

0.025

0.030

Xe26+

Xe27+

picoAmperes of isotope-resolved Xe27+ ions

Single ionization of XeSingle ionization of Xeq+q+ ions: overview ions: overview

100 1000

1

10

100

Cro

ss s

ectio

n (

Mb

)

Electron energy ( eV )

Xe1to2E Xe2to3E Xe3to4E Xe4to5E Xe5to6E Xe6to7E Xe7to8E Xe8to9E Xe9to10E Xe10to11E Xe11to12E Xe12to13E Xe13to14E Xe14to15E Xe15to16E

A. Borovik jr., M. Gharaibeh, S. Schippers, and A. Müller, 2007

Electron-ion collisions at heavy-ion storage ringsElectron-ion collisions at heavy-ion storage rings

from a c c e le ra tord ip o leq ua d rup o le

se p tum

extra c te db ea m

injec tiona nd

extra c tion

ion b e a md irec tion

e le c tron c o o le r

Ele c tron ta rg e t sec tion

c o llision p rod uc td etec to rs

c ha rg e dfra g m entc o unting

b ea m p rofilem o nito r

(hor./ve rt.)ion c urre ntm o nito r

Sc ho ttkyp ic k-up

m o le c ula rfra g m entim a g ing

5m

ind uc tio na c c e le ra tor

ionizationrecombination

recombination

Storage ring TSR at Max-Planck-Institut für Storage ring TSR at Max-Planck-Institut für Kernphysik, Heidelberg, Kernphysik, Heidelberg, where metastables die outwhere metastables die out

Dielectronic Dielectronic recombina- recombina- tion of Fe L-tion of Fe L-shell ions: shell ions: a jointa jointUS-German US-German project for project for astrophysicsastrophysics

Fe22+

Fe19+

Fe17+ Fe18+

Fe20+

Fe21+

Columbia-Astrophysics Laboratory

Justus-Liebig-Universität Giessen

Max-Planck-Institut für Kernphysik

Recombination of FeRecombination of Fe13+13+ ions finalized: overview ions finalized: overview

0 10 20 30 40 5010-10

10-9

10-8

10-7

Electron-ion collision energy (eV)

Rec

ombi

natio

n ra

te c

oeff.

(cm

3 s-1) 3s2 3p 2P 3s2 3d 2D3/2 nl''' series

3s2 3p 2P 3s 3p2 2P3/2

nl''' series

3s2 3p 2P 3s 3p2 2P1/2

nl''' series

3s2 3p 2P 3s 3p2 2S1/2

nl''' seriesn=8

n=7

n=7

n=7

E. W. Schmidt, S. Schippers, A. Müller, M. Lestinsky, F. Sprenger, M. Grieser, R. Repnow,A. Wolf, C. Brandau, D. Lukić, M. Schnell, D. W. Savin, Astrophys. J. 641, L157 (2006)

Recombination of FeRecombination of Fe13+13+ ions : Rydberg series ions : Rydberg series

50 550.0

5.0x10-10

1.0x10-9

1.5x10-9

2.0x10-9

Electron-ion collision energy (eV)

Rec

ombi

natio

n ra

te c

oeff.

(cm

3 s-1) 3s2 3p 2P 3s2 3d 2D

3/2 nl''' series

n=7

E. W. Schmidt, S. Schippers, A. Müller, M. Lestinsky, F. Sprenger, M. Grieser, R. Repnow,A. Wolf, C. Brandau, D. Lukić, M. Schnell, D. W. Savin, Astrophys. J. 641, L157 (2006)

Recombination of FeRecombination of Fe13+13+ ions : ions : huge resonances at very low energieshuge resonances at very low energies

0.01 0.1 1 10 1000

10

20

30

40

Schmidt et al., experiment, 2006 Badnell, theory, 2006

Rat

e co

effic

ient

( 1

0-9 c

m3 s-1

)

Electron-ion collision energy ( eV )

Fe13+(3s2 3p 2P)

E. W. Schmidt, S. Schippers, A. Müller, M. Lestinsky, F. Sprenger, M. Grieser, R. Repnow,A. Wolf, C. Brandau, D. Lukić, M. Schnell, D. W. Savin, Astrophys. J. 641, L157 (2006)

Recombination of FeRecombination of Fe13+13+ ions : ions : plasma rate coefficientsplasma rate coefficients

0.1 1 10 100

10-10

10-9

10-8

Schmidt et al., experiment Arnaud & Raymond,

compilation 1992 Netzer, deliberate suggestion 2004 Badnell 2006

Electron temperature (eV)

Rat

e co

effie

nt (

cm

3 s-1 )

collisionallyionizedplasma

photo-ionizedplasma

E. W. Schmidt, S. Schippers, A. Müller, M. Lestinsky, F. Sprenger, M. Grieser, R. Repnow,A. Wolf, C. Brandau, D. Lukić, M. Schnell, D. W. Savin, Astrophys. J. 641, L157 (2006)

3 → 3 DR of Fe3 → 3 DR of Fe14+14+: plasma rate coefficients: plasma rate coefficients

D. Lukić, M. Schnell, D. W. Savin C. Brandau, E. W. Schmidt, S. Böhm, A. Müller, S. Schippers, M. Lestinsky, F. Sprenger, A. Wolf, Z. Altun, N. R. Badnell, Astrophys. J. 664, 1244 (2007)

experiment, all

experiment, minus 2

Arnaud&Raymond recommended

Netzer modified

MCBP theory

RR, Arnaud&Raymond

recommended

effect of high-n extrapolation

3 → 3 DR of Si3 → 3 DR of Si3+3+: plasma rate coefficients: plasma rate coefficients

0 1 2 3 4 5 6 7 8 9-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

2p6 3d

2 1 G

Rec

ombi

natio

n ra

te c

oeff.

(10-1

0 cm

3 s-1)

Electron-ion collision energy (eV)

2p6 3d

2 3 F

n=4 5 6 7 8

3p nl resonances

0.1 1

0.0

0.5

1.0

E. W. Schmidt, D. Bernhardt, A. Müller, S. Schippers, S. Fritzsche, J. Hoffmann, A. S. Jaroshevich, C. Krantz, M. Lestinsky, D. A. Orlov, A. Wolf, D. Lukić, D. W. Savin, Phys. Rev. A 2007, in the press

SummarySummaryElectron-impact ionization of ions:Cross sections for single and multiple ionization of Xeq+ ions, q=1,2,…,15,… and of Snq+ ions, q=1,2,… are being measured in Giessen and analysis of the experimental results is underway. ((

Dielectronic recombination:resonance strengths and plasma rate coefficients are determined in high-resolution storage ring experiments.Data for Fe13+ and Fe14+ have been obtained and published. Data on Si3+ have been finalized and are being published.

Preliminary data are available for Fe7+ and Fe8+. Their analysis is underway.

OutlookOutlook

Electron-impact ionization of ions:

Complete cross section measurements for single and multiple ionization of Xeq+ ions, q=1,2,…,15,… and of Snq+ ions, q=1,2,…

Dielectronic recombination:

Finalize data analysis and obtain resonance strengths and plasma rate coefficients for Fe7+ and Fe8+. Extend the series to other ions in the iron iso-nuclear sequence.