recombination reactions and commissioning of desiree

Recombination Recombination reactions and reactions and commissioning of commissioning of DESIREEDESIREE

Åsa Larson & Mats Larsson

OutlineOutline

• Recombination reactions

• The H2 system

• The HeH system

• The BeH system

• Commissioning of DESIREE

Åsa

Mats

Recombination Recombination reactionsreactions

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


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**


AB+

AB*

A++B-

A* +B

A++B

A+B+


Resonant ion-pair formation (RIP)Resonant ion-pair formation (RIP)

-*- BAABeAB v

AB**


AB+

AB*

A++B-

A* +B

A++B

A+B+


Vibrational excitation/deexcitation (VE)Vibrational excitation/deexcitation (VE)

-- e'ABeAB vv

Direct/resonant

AB**


AB+

AB*

A++B-

A* +B

A++B

A+B+


Dissociative excitation (DE)Dissociative excitation (DE)

-*

--*-

eBAAB

eBAeABeAB v

Direct/resonant

AB**


AB+

AB*

A++B-

A* +B

A++B

A+B+

Anion-cation collisions

Mutual neutralization (MN)Mutual neutralization (MN)

AB**

BAABBA **-


AB+

AB*

A++B-

A* +B

A++B

A+B+


Double charge transfer (DCT)Double charge transfer (DCT)

AB**

BAABBA -*-


AB+

AB*

A++B-

A* +B

A++B

A+B+


AB**

Associative ionization (AI)Associative ionization (AI)

-*- e'ABABBA v


AB+

AB*

A++B-

A* +B

A++B

A+B+


AB**

Electron detachment (ED)Electron detachment (ED)

-*- eB AABBA

The HThe H22 system system

HH+++H+H-- collisions collisions

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+


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

)


H+H(n=2)

42

1)(

RRVRV th


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).

H+ + H-

Total neutralization cross section


Mutual neutralizationMutual neutralization

H+ + H-

Branching ratios


Mutual neutralizationMutual neutralization

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.

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!


Differential cross section Isotope dependence

,E

d

d


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!

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


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).



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


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).



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


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).


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).


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


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!

The HeH systemThe HeH system

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

)


Combining structure and electron scattering calculations

Very highly excited states!


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).

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,

''

'',

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


Strict diabatic transformation

Quantum study of high-energy DR, RIP andMN. Inclusion of autoionization.

The BeH systemThe BeH system

DR of BeHDR of BeH++

Direct DR(Previous CRP meeting)

Indirect mechanism + VE:

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.


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


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

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

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

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

recombination reactions and commissioning of desiree

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