Dissociative Recombination of diatomic cations with electrons in cold plasma
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Workshop on Atomic and Molecular Data for fusion Trieste 2006
Dissociative Recombination of diatomic cations with electrons in cold plasma
Francois Olivier WAFFEU TAMORepublic of CAMEROUN
Thesis in alternance (2004 - present)
Ioan F. SCHNEIDERUniversity of Havre, LMPG
FRANCE
Ousmanou MOTAPON University of Douala, CEPAMOQ
CAMEROUN
TSR
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e- + AB+ A + B*
Variation of electronic
density, ne
ωplasma ~ (ne)1/2
Reflexion of wave if ωwave < ωplasma
neutrals in excited states
Emission of light
Rich Chemistry
Many applications
DR is an important process in cold plasma !!!
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Mechanisms e- + AB+ ??? A + B*
Direct process
Direct capture in aDissociative state(Doubled excited state)
AB**
Indirect process
Temporary capture in
a Rydberg state
(Mono-excited state)
AB*
Resonances !!!
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Quasi-diabatic Representationof relevant molecular states
AB**
AB*
AB+
A + B*
A + B+
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Multichannel Quantum Defect Theory calculations (I)
InputAB+ (Ni
+,vi+,…)
AB* @ quantum defect μ
AB** @ Final states of atoms, (N,…)
Electronic couplings (BO)
Incident electron, l(0,2)
Output, σNi+
,vi+
,N (v )
ObservableRates
coefficientsα = <σv>
Keep in mindEach rovibrational level N+,v+ of
target ion can be viewed as the limit of a series of rovibrational levels of
Rydberg states.
For a given Ni+ ,
│Ni+ - l│≤ N ≤│ Ni
+ + l │
and N is also coupled to N+ given by: │N- l│≤ N+ ≤│ N+ l │
Peak
Assignments !!!
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Procedure
for a given initial state of ion
σ Ni+
,vi+(v)= ∑N σNi
+,vi
+,N (v)
α Ni+
,vi+(Ed)= < σ Ni
+,vi
+.v>
averaged Boltzmann rate coefficients
α obs ≡ ∑ α Ni+
,vi+
,(Ed) . Pi
General Assumptions
1. Maxwell anisotropic distribution for velocity of the electrons , f
2. Boltzmann distribution, Pi of ions are on the lower rovibra- tionnal states
Multichannel Quantum Defect Theory calculations (II)
Local rates
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M. Larsson, Int. J. Mass Spectrom. Ion Processes 149/150, 403 (1995)
m, electron mass v , center-of-mass velocity vd , detuning velocity at the center of velocity distribution k, the boltzmann constant Te, electronic temperature ( experimental conditions)
ANISOTROPIC Maxwell distribution function, f
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MQDT vs ExperimentsHD+ / HD (vi
+ = 0 & Ni+ =0,...,12)
Interpretation of the resonance structure
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Ni+=1
• l = 0 (s wave)N=1
• l = 2 (d wave)N=1,3
N=1,3
• N=1 N+=1,3
• N=3N+= 1,3,5
bars ≡ predicted resonances
Ed(res) = E(ryd) - E(Ni
+,vi+)
Approximation !!!
E(ryd) = E(N+,v+) – Ryd*[2(n-μl)2]-1
σ.v ( N=1)
σ.v ( N=3)
σ.v & α ( N=1,3)log scale
σ.v & α ( N=1,3)lin scale
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MQDT vs ExperimentsHD+ / HD (vi
+ = 0 & Ni+ =0,...,12)
Interpretation of the resonance structure About to be published
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Boundary of the fusion plasma
M. C. Stroe, M. Fifirig, F. O. Waffeu Tamo, O.Motapon, O. Crumeyrolle, G. Varin-Bréant, A. Bultel, P. Vervisch, A. Suzor-Weiner et I. F. Schneider, “Reactive collisions between electrons and molecular hydrogen cation isotopomers: cross sections and rate coefficients for HD+ and DT+, accepted in APID 13.
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Boundary of the fusion plasma (I) HD+ / HD
Indirect process
&
Rotationnal effects
Direct process !
Rotationnal effects neglected
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Boundary of the fusion plasma (II) DT+ / DT
Direct process !
Rotationnal effects neglected
Indirect process
&
Rotationnal effects
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Boundary of the fusion plasma (III) HD+ / HD & DT+ / DT
Direct process !
Rotationnal effects neglected
Indirect process
&
Rotationnal effects
thin ≡HD+/HD
bold ≡ DT+/DT
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Boundary of the fusion plasma (IV) HD+ / HD (DR,EC, SEC & IC)
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Thanks for Your attention !
Special Thanks to Organizers & Lecturers !