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 Müller
Institut für Atom- und MolekülphysikInstitut für Atom- und Molekülphysik
JU STU S-LIEB IG - 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 sections
absolute 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
-18 c
m2 )
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 (
Mb
)
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 (
Mb
)
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
ect
ion
( 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
Cro
ss s
ectio
n (
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
ect
ion
( 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
Cro
ss s
ectio
n 10
11 ( 1
0-18 c
m2 )
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
Cu
rre
nt
( n
A)
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
ect
ion
(
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 tedb 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 e tec 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)
Re
com
bin
atio
n r
ate
co
eff
. (c
m3 s
-1) 3s2 3p 2P 3s2 3d 2D
3/2 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)
Ra
te c
oe
ffie
nt
( c
m3 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
-10 c
m3 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
SummarySummary
Electron-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.
Top Related