REACTIVE COLLISIONS BETWEEN ELECTRONS AND MOLECULAR … · 2006. 9. 1. · ☺ab initio...
Transcript of REACTIVE COLLISIONS BETWEEN ELECTRONS AND MOLECULAR … · 2006. 9. 1. · ☺ab initio...
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AMDER, Trieste 2006
Ousmanou MOTAPON
Department of PhysicsFaculty of Science
University of Douala (CAMEROON)
REACTIVE COLLISIONS BETWEEN ELECTRONS AND MOLECULAR CATIONS
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F. O. Waffeu Tamo(PhD, University of Douala andUniversité du Havre, France)
V. Ngassam(former PhD, Douala and Université Paris-Sud, … Presently @ University of Davis)
Prof. I.F. Schneider, Université du Havre, France,
Prof. A. Suzor-Weiner, Université Paris-Sud, France,
Dr. M. Fifirig, University of Bucharest, Romania
A. Bultel, P Vervisch, University of Rouen
J. Tennyson, University College, London, UKL. Pichl, University of Aizu, Japan
COLLABORATIONS
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AB+(v')+e-
v' < vAB+(v')+e-
v' > v
AB** @ AB*
A(n) + B(n')
AB+ (v ) + e-
DR
EC
ICSEC
WHATREACTIONS ?
A+B++e-
DE
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� H2+ and isotopomers(HD+, HT+, etc.)
� NO+, CO++, CO+, Ne2+, etc.
� CxHy+, etc …
WHAT IONS
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� Important processes for :– interstellar medium– planetary atmospheres – fusion plasma devices– plasmas of technological interest ( displays, combustion )– plasma assisted depollution– plasma of aeronautical interest ( re-entry of spacecrafts, etc.)
� Rôle of the electron-ion collisions :– ion and electron densities– source of excited atoms and molecules – heating (kinetic energy of fragments)
WHAT FOR?
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An Example: Atomic Collisions in PLASMASof ATMOSPHERIC and ENERGETIC interest
Injection of cold gaz
(AB molecules)
Produced plasma
(e-, AB+, others)
Chemistry of the plasma :governed by the interaction of chargedparticles
⇒ Need to know how e- and AB+ interact…
2
[ ] [ ]( ) ( ) [ ] RayColliiii XJdivVXdivtX
−
•+−=+
∂∂ rr
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� TWO STEP TREATMENT:
�☺ ab initio calculations of the molecularstructure, the electronic interactions between molecularstates, the quantum defects,… (R-matrix, complex Kohnvariational method, quantum chemistry…)
�☺ Dynamics:MQDT, Wave packet technique
►Cross sections & rate coefficients(Comparison vs Experiments)
THEORY
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DDDIIIRRREEECCCTTT
dissociative state
AB**
e + AB+ A* + B
AB*
bound state
IIINNNDDDIIIRRREEECCCTTT
MECHANISMS
AB++e, A+B++e
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MECHANISMSExampleExample of relevant states for HDof relevant states for HD++/HD system/HD system
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MECHANISMS
AB**
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Method: Multichannel Quantum Defect Theory
dissociation
Reaction zone and Reaction zone and
different channelsdifferent channels
Dissociative excitation
ionization
aReaction
zone
AB**
••Time Time independentindependentmethodmethod((SuzorSuzor--WeinerWeiner19801980,,Seaton, Seaton, Fano, Fano, JungenJungen, Green,, Green,……19501950--90)90)
•Distinction betweenshort and long range interactions
•Concept of channel
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� Ionization channels :
Dynamics:: Wave functions and interactions
� Elimination of closed channels – resonances� The diffusion matrix S – open channels
{ }, , ( ) ( , ) cos ( ) ( , ) si ( )ni v i v iR f r rR Rgχ ε π ε πµ µ+ Ψ = Φ × −� Dissociation channels:
( , )d d dF E RχΨ = Reaction matrix K – all channels
0
1V V
EK
HK= +
− Calculation of the reaction matrix K
0
1K V V V
E H= + + ⋅⋅⋅
−
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THEORETICAL FRAMEWORK Main steps in the MQDT approach
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THEORETICAL FRAMEWORK Main steps in the MQDT approach
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Computations, advances in method, comparison with experiment
NO+
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COMPUTATIONS vs MEASUREMENTS: NO +/NO
COUPLINGS
STATES
Tennyson et al 1996-2000, Electron-ion scattering: R-matrix method
More dissociative channels
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Cross section for INELASTIC COLLISIONS of NO+ ions with electrons
COMPUTATIONS vs MEASUREMENTS: NO +/NO
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Comparison with ASTRID
Schneider et al 2000
More dissociative channels
COMPUTATIONS vs MEASUREMENTS: NO +/NO
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Maxwell isotropic rate coefficients of DISSOCIATIVE RECOMBINATION Experiment: Mostefaoui et al. 1999
COMPUTATIONS vs MEASUREMENTS: NO +/NO
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COMPUTATIONS vs MEASUREMENTS: NO +/NO
Motapon et al 2006
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COMPUTATIONS vs MEASUREMENTS: NO +/NO
Motapon et al 2006, Plasmas Sources Sc.Technol. 15, 23
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Computations, advances in method, comparison with experiment
H2+
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Results: DR rate coefficients for H2+
Ngassam et al. 2003, PRA 68, 032704
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DRCOMPUTATIONS vs MEASUREMENTS H2+/H2
0,02 0,04 0,06 0,08 0,1
Energy of the incident electron (eV)
2,00×10-9
4,00×10-9
6,00×10-9
8,00×10-9
1,00×10-8
1,20×10-8
1,40×10-8
1,60×10-8
1,80×10-8
2,00×10-8
Theory, no rotationTheory with rotation, ortho-para effect includedTheory with rotation, no ortho-para effectExperiment
Rat
e c
oeffi
cien
t (cm
3 s-1
)O. Motapon et al 2006 , To be published
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Super-elastic collisionsCOMPUTATIONS vs MEASUREMENTS H2+/H2
1e-05 0,0001 0,001 0,0110-10
10-9
10-8
10-7
Rat
e co
effic
ient
s (c
m3 /s)
Theory with rotationExperimentTheory, no rotation
1e-05 0,0001 0,001 0,01 0,1
Energy of the incident electron (eV)
(a) (b)
O. Motapon et al 2006, To be published
DR, v=1
SEC, v=1
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The DISSOCIATIVE autoionization
Motapon et al 2004, DR6 & ECAMP8
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Discretization of the vibrational continuum (Takagi 2002):
� splitting into thin N energy bands [Ei, Ei+1], i=0,1,...,N
� building of "quasiquasi--discretediscrete" wave functions: energy-normalized solutions χE(R) of the Schrödinger equation
↓re-normalization in the coordinate space:
,)(1
)( 11
EEE
EdERR ii
i
iEi
−=∆∫∆= +
+χχ
ADVANCES IN THEORY: Dissociative Excitation
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ADVANCES IN THEORY: Dissociative Autoionization
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ADVANCES IN THEORY: DissociativeExcitation
,)(1
)( 11
EEE
EdERR ii
i
iEi
−=∆∫∆= +
+χχ
Motapon et al 2004, DR6 & ECAMP8
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•••• Dissociative recombination: satisfactorymodelling with MQDT•••• Superelastic collisions:somediscrepancies with experiment for H2+
Contribution of rotational effects … promising! • High energy: Dissoc. excitation:
successfulmodelling at intermediate energyagreementwith some experiments
Refinements on the way !
� Data compilation for H2+ and isotopomers���� APID 13� Extensive calculations for NO+: Radiative collision model of air plasma for
earth re-entry problem (Motapon et al. 2006, Plasmas Sources Sc.Technol. 15, 23, Bultel et al. 2006, Phys.Plasmas13, 043502)
� CO+, CxHy+ & Angular distribution …
IN SHORT …
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