recombination reactions and commissioning of desiree
DESCRIPTION
Recombination reactions and commissioning of DESIREE. Åsa Larson & Mats Larsson. Outline. Recombination reactions The H 2 system The HeH system The BeH system Commissioning of DESIREE. Åsa. Mats. Recombination reactions. Recombination reactions …. - PowerPoint PPT PresentationTRANSCRIPT
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Recombination Recombination reactions and reactions and commissioning of commissioning of DESIREEDESIREE
Åsa Larson & Mats Larsson
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OutlineOutline
• Recombination reactions
• The H2 system
• The HeH system
• The BeH system
• Commissioning of DESIREE
Åsa
Mats
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Recombination Recombination reactionsreactions
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Recombination reactions …Recombination reactions …
… relevant for the fusion plasma of the divertor.
•Light atomic/molecular ions H, He, Be, …,O
• Relative low energies (E<20 eV)
• Different isotopes
• Different vibrational states v=0,1,2,… • Total cross section, final state distributions and differential cross section
• H- might be present
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Recombination reactions …Recombination reactions …
BAABeAB **- v
Dissociative recombination (DR)Dissociative recombination (DR)
AB+A++B-
A* +B
A++B
A+B+
Electron-molecular ion collisions
Direct/indirect
AB*
AB**
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Recombination reactions …Recombination reactions …
AB+
AB*
A++B-
A* +B
A++B
A+B+
Electron-molecular ion collisions
Resonant ion-pair formation (RIP)Resonant ion-pair formation (RIP)
-*- BAABeAB v
AB**
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Recombination reactions …Recombination reactions …
AB+
AB*
A++B-
A* +B
A++B
A+B+
Electron-molecular ion collisions
Vibrational excitation/deexcitation (VE)Vibrational excitation/deexcitation (VE)
-- e'ABeAB vv
Direct/resonant
AB**
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Recombination reactions …Recombination reactions …
AB+
AB*
A++B-
A* +B
A++B
A+B+
Electron-molecular ion collisions
Dissociative excitation (DE)Dissociative excitation (DE)
-*
--*-
eBAAB
eBAeABeAB v
Direct/resonant
AB**
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Recombination reactions …Recombination reactions …
AB+
AB*
A++B-
A* +B
A++B
A+B+
Anion-cation collisions
Mutual neutralization (MN)Mutual neutralization (MN)
AB**
BAABBA **-
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Recombination reactions …Recombination reactions …
AB+
AB*
A++B-
A* +B
A++B
A+B+
Anion-cation collisions
Double charge transfer (DCT)Double charge transfer (DCT)
AB**
BAABBA -*-
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Recombination reactions …Recombination reactions …
AB+
AB*
A++B-
A* +B
A++B
A+B+
Anion-cation collisions
AB**
Associative ionization (AI)Associative ionization (AI)
-*- e'ABABBA v
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Recombination reactions …Recombination reactions …
AB+
AB*
A++B-
A* +B
A++B
A+B+
Anion-cation collisions
AB**
Electron detachment (ED)Electron detachment (ED)
-*- eB AABBA
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The HThe H22 system system
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HH+++H+H-- collisions collisions
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0 10 20 30 40 50-0.75
-0.70
-0.65
-0.60
-0.55
-0.50
-0.45
-0.40
H+H+
H-+H+
H+H(n=3)
En
erg
y (H
)
Internuclear distance (a0)
H+H(n=2)
H2 adiabatic potential energy curves symmetry1Σg+
The HThe H22 system system
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H2 adiabatic potential energy curves symmetry1Σg+
0 10 20 30 40 50-0.75
-0.70
-0.65
-0.60
-0.55
-0.50
-0.45
-0.40
H+H+
H-+H+
H+H(n=3)
En
erg
y (H
)
Internuclear distance (a0)
H+H(n=2)
42
1)(
RRVRV th
The HThe H22 system system
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Mutual neutralizationMutual neutralization H+ + H- →H(n) + H
• Calculate the cross section for the mutual neutralization reaction at low collision energies (< 100 eV).
• Fully quantum mechanical – electronic – vibrational – rotational
• Accurate structure calculations FCI (11s,8p7d,2f) → [9s,8p,7d,2f]
• Include all states up the H(n=3)+H and H+ + H-
• Strict diabatization
• Identical nuclei
• Log-derivative method
H+ + H-
M. Stenrup, Å. Larson and N. Elander, Phys. Rev. A 79, 012713 (2009).
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H+ + H-
Total neutralization cross section
M. Stenrup, Å. Larson and N. Elander, Phys. Rev. A 79, 012713 (2009).
Mutual neutralizationMutual neutralization
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H+ + H-
Branching ratios
M. Stenrup, Å. Larson and N. Elander, Phys. Rev. A 79, 012713 (2009).
Mutual neutralizationMutual neutralization
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H+ + H-
Double charge transferDouble charge transfer H+ + H- →H- + H+
J. Zs. Mezei, M. Stenrup, N. Elander and Å. Larson, Phys. Rev. A 82, 014701 (2010).
Good agreement with other theoretical studies but a factor of 10 larger than measured ones.
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H+ + H- Mutual neutralizationMutual neutralization
Differential cross section
A quantum study is needed!
,E
d
d
Will
be
com
pared
with
new e
xper
imen
ts b
y X.
Urbai
n!
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H+ + H- Mutual neutralizationMutual neutralization
Differential cross section Isotope dependence
,E
d
d
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H+ + H- Mutual neutralizationMutual neutralization
Why quantum? Semi-classical Landau-Zener study
H+H(n=2)
H+H(n=3)
H- +H+
l
lijij EPl
EE 12
2)(
Very sensitive to crossing points and coupling strengths!
Try different methods to obtain couplings
Use
H+ +
H- a
s
a te
st s
yste
m!
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H+ + H- Mutual neutralization
Compare with QM cross section
0.01 0.1 1 10 100
10-14
10-13
10-12
10-11
Cro
ss s
ectio
n (c
m2 )
Energy (eV)
Stenrup et al.
and branching ratios
0 20 40 60 80 100
0.0
0.2
0.4
0.6
0.8
1.0
Energy (eV)
B
ranc
hing
rat
ios
n=2 n=3
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H+ + H- Mutual neutralization
Semi-empirical method: “Olson 1”
xxif RRH 99.0exp5.791.0exp0.82
2
2
1
I Effective ionization potential of electron which is transferred fromreactants (electron negativity)
0.01 0.1 1 10 100
10-14
10-13
10-12
10-11
Cro
ss s
ect
ion
(cm
2 )
Energy (eV)
Stenrup et al. SC using "Olson1"
0 20 40 60 80 1000.0
0.2
0.4
0.6
0.8
1.0
Bra
nch
ing
ra
tios
Energy (eV)
n=2 n=3
R. E. Olson, J. R. Peterson and J. Moseley, J. Chem Phys. 53 3391 (1970).
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H+ + H- Mutual neutralization
Semi-empirical method: “Olson 2”
c
RIIAc
c
RAH xx
if 21 ,2
,exp
2
2
2
I Effective ionization energy of the electron in the product state
0.01 0.1 1 10 100
10-14
10-13
10-12
10-11
Stenrup et al. SC using "Olson2"
Cro
ss s
ect
ion
(cm
2 )
Energy (eV)0 20 40 60 80 100
0.0
0.2
0.4
0.6
0.8
1.0
Bra
nchi
ng r
atio
s
Energy (eV)
n=2 n=3
R. E. Olson, F. T. Smith and E. Bauer, Appl. Opt. 10 1848 (1971).
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H+ + H- Mutual neutralization
Semi-empirical method: “Olson 3”
xif
ifif RRII
HHRRH
2
1 , ,857.0exp044.1 *
21
****
0.01 0.1 1 10 100
10-14
10-13
10-12
10-11
Stenrup et al. SC using "Olson3"
Cro
ss s
ect
ion
(cm
2 )
Energy (eV)
0 20 40 60 80 1000.0
0.2
0.4
0.6
0.8
1.0
Bra
nchi
ng r
atio
s
Energy (eV)
n=2 n=3
R. E. Olson, J. Chem Phys. 56 2979 (1972).
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H+ + H- Mutual neutralization
Using the “Landau-Herring method”
xx
xif R
ll
lR
R
AH
exp
/11/1
121exp4
2/2/1
2
222
“Smirnov”
0.01 0.1 1 10 100
10-14
10-13
10-12
10-11
Stenrup et al. SC using "Smirnov"
Cro
ss s
ectio
n (
cm2 )
Energy (eV)0 20 40 60 80 100
0.0
0.2
0.4
0.6
0.8
1.0
Energy (eV)
B
ran
chin
g r
atio
s
n=2 n=3
B. M. Smirnov, Sov. Phys. Dokl. 10 218 (1965); 12 242 (1967).
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H+ + H- Mutual neutralization
Using the “Landau-Herring method”
2/1/11/1 /11/12 ,exp2
1 llARDRAAH cxxciif
“Janev”
0.01 0.1 1 10 100
10-14
10-13
10-12
10-11
Cro
ss s
ect
ion
(cm
2 )
Energy (eV)
Stenrup et al. SC using "Janev"
R. K. Janev, Adv. At. Mol. Phys. 12 1 (1976).
0 20 40 60 80 100
0.0
0.2
0.4
0.6
0.8
1.0
Energy (eV)
B
ranc
hing
rat
ios
n=2 n=3
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H+ + H- Mutual neutralization
Ab initio 2x2 transformation:
RdRfRRR
RR
R
ij~~~
)( ,)(cos)(sin
)(sin)(cos ,
TTVTU 1
0.01 0.1 1 10 100
10-14
10-13
10-12
10-11 Stenrup et al. SC using "ATD"
Cro
ss s
ect
ion
(cm
2 )
Energy (eV)0 20 40 60 80 100
0.0
0.2
0.4
0.6
0.8
1.0
Energy (eV)
B
ranc
hing
rat
ios
n=2 n=3
Conclusion: Conclusion: Janev and ATD work best!
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The HeH systemThe HeH system
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Adiabatic resonant states of HeH (FCI)
5 10 15 20 25 30 35 40 45
-2.9
-2.8
-2.7
-2.6
-2.5
En
erg
y (H
)
Internuclear distance (a0)
Combining structure and electron scattering calculations
Very highly excited states!
The HeH systemThe HeH system
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Resonant DEResonant DE
(Results from previous CRP meeting)
0 5 10 15 20 25 30 35 40
0.0
2.0x10-18
4.0x10-18
6.0x10-18
8.0x10-18
1.0x10-17
1.2x10-17
Cro
ss s
ectio
n (c
m2 )
Energy (eV)
Experiment Total
2+
2 2
HeH+ + e- →HeH* →He + H+ + e-
C. Strömholm et al., PRA 54 3086 (1996).
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Direct DEDirect DE HeH+ + e- →(HeH+)* + e- →He+ + H + e-
C. Strömholm et al., PRA 54 3086 (1996).
dRRERE vijij 2,
Feshbach resonances!?
Remove the resonancecontribution from the T-matrix
Develop a t-dep method
RREET
EEtR
vijmlml
mlmlij
,',
',,0,
''
'',
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22 24 26 28 30 32 34 36 38 400.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
No
n-a
dia
ba
tic c
ou
plin
gs (
a.u
.)
Internuclear distance (a.u.)
Non-adiabatic couplings are presently calculated
The HeH systemThe HeH system
Strict diabatic transformation
Quantum study of high-energy DR, RIP andMN. Inclusion of autoionization.
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The BeH systemThe BeH system
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DR of BeHDR of BeH++
Direct DR(Previous CRP meeting)
Indirect mechanism + VE:
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Mutual neutralization?Mutual neutralization? Be+ + H- →BeH*→Be* + H
J. Pitarch-Ruiz et al., J Chem Phys. 129 054310 (2008)
Avoided crossings with 9 states of 2Σ+ symmetry
Ab initio calculations are hard!
Semi-classical LZ methodwith the Janev couplings.
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Mutual neutralization?Mutual neutralization? Be+ + H- →BeH*→Be* + H
0.01 0.1 1 10 100
10-13
10-12
10-11
Cro
ss s
ect
ion
(cm
2 )
Energy (eV)
Be++H-
Be++D-
Be++T- Large cross section
Small isotope effect
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Mutual neutralization?Mutual neutralization? Be+ + H- →BeH*→Be* + H
Many states contribute
0 20 40 60 80 1000.0
0.2
0.4
0.6
0.8
1.0
Bra
nch
ing
ra
tio
Energy (eV)
bran1 bran2 bran3 bran4 bran5 bran6 bran7 bran8 bran9
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Commissioning of Commissioning of DESIREEDESIREE
● R. D. Thomas, H. T. Schmidt, G. Andler, M. Björkhage, M. Blom, L. R. D. Thomas, H. T. Schmidt, G. Andler, M. Björkhage, M. Blom, L.
Brännholm, E. Bäckström, H. Danared, M. Gatchell, N. Haag, P. Halldén, Brännholm, E. Bäckström, H. Danared, M. Gatchell, N. Haag, P. Halldén,
Dag HanstorpDag Hanstorp
F. Hellberg, H. A. B. Johansson, A. Källberg, G. Källersjö, M. Larsson, S. F. Hellberg, H. A. B. Johansson, A. Källberg, G. Källersjö, M. Larsson, S.
Leontein, L. Liljeby, P. Löfgren, B. Malm, S. Mannervik, A. Paál, Leontein, L. Liljeby, P. Löfgren, B. Malm, S. Mannervik, A. Paál,
P. Reinhed, K. G. Rensfelt, S. Rosén, K. Schmidt, A. Simonsson, M. Stockett, P. Reinhed, K. G. Rensfelt, S. Rosén, K. Schmidt, A. Simonsson, M. Stockett,
J. Weimer, H. Zettergren, and H. CederquistJ. Weimer, H. Zettergren, and H. Cederquist
● Department of Physic, Stockholm UniversityDepartment of Physic, Stockholm University
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160° Bend
Quadrupole doublet
From platform 2
Outer vessel
Inner vessel
Thermal screen
10° Deflection
Detector for neutral reaction products
Drift tube merging section
Variable deflections
Port for laser light
From platform 1
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Next stepNext step
● Inject and store ions at room temperature in the asymmetric ring
● Cool down the ring again to 15 K
● Start merged beam experiments: H+ + H