Dissociative Recombination of diatomic cations with electrons
in cold plasma
TSR
Francois Olivier WAFFEU TAMO
Republic of CAMEROUN
Thesis in alternance (2004 - present)
Ioan F. SCHNEIDER
University of Havre, LMPG
FRANCE
Ousmanou MOTAPON
University of Douala, CEPAMOQ
CAMEROUN
Workshop on Atomic and Molecular Data for
fusion Trieste 2006
e- + AB+

Variation of electronic
density, ne
ωplasma ~ (ne)1/2
Reflexion of wave if ωwave < ωplasma
A + B*

neutrals in excited states
Emission of light
Rich Chemistry
Many applications
DR is an important process
in cold plasma !!!
Mechanisms
e- + AB+

Direct process
Direct capture in a
Dissociative state
(Doubled excited state)
AB**
A + B*
???

Indirect process
Temporary capture in
a Rydberg state
(Mono-excited state)
AB*
Resonances !!!
Quasi-diabatic Representation
of relevant molecular states
AB
+
A + B+
A + B*
AB*
AB**
Multichannel Quantum Defect Theory
calculations (I)

AB+ (Ni+,vi+,…)
AB* @ quantum defect μ
AB** @ Final states of atoms, (N,…)
Electronic couplings (BO)
Incident electron, l(0,2)

Output,
Observable
Keep in mind
Each rovibrational level N+,v+ of
target ion can be viewed as the limit of
a series of rovibrational levels of
Rydberg states.

Input
σNi+,vi+,N (v )
Rates
coefficients
α = <σv>
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 !!!
Multichannel Quantum Defect Theory
calculations (II)

Procedure

General Assumptions
1.
Maxwell anisotropic distribution
for velocity of the electrons , f
2.
Boltzmann distribution, Pi of
ions are on the lower rovibrationnal states
for a given initial state of ion
σ Ni+,vi+(v)= ∑N σNi+,vi+,N (v)
α Ni+,vi+(Ed)= < σ Ni+,vi+.v>
Local rates
averaged Boltzmann rate coefficients
α obs ≡ ∑ α Ni+,vi+,(Ed) . Pi
ANISOTROPIC Maxwell distribution
function, f
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)
MQDT vs Experiments
HD+ / HD (vi+ = 0 & Ni+ =0,...,12)
Interpretation of the resonance structure

•
•
Ni+=1
l = 0 (s wave)
N=1
l = 2 (d wave)
N=1,3
N=1,3
•
•
N=1
N+=1,3
N=3
N+= 1,3,5
σ.v & α ( N=1,3)
lin scale
σ.v & α ( N=1,3)
log scale
σ.v ( N=3)
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)
MQDT vs Experiments
HD+ / HD (vi+ = 0 & Ni+ =0,...,12)
Interpretation of the resonance structure
About to be published
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.
Boundary of the fusion plasma (I)
HD+ / HD
Direct process !
Rotationnal effects
neglected
Indirect process
&
Rotationnal effects
Boundary of the fusion plasma (II)
DT+ / DT
Direct process !
Rotationnal
effects neglected
Indirect process
&
Rotationnal effects
Boundary of the fusion plasma (III)
HD+ / HD & DT+ / DT
Direct process !
Rotationnal
effects neglected
thin ≡HD+/HD
bold ≡ DT+/DT
Indirect process
&
Rotationnal effects
Boundary of the fusion plasma (IV)
HD+ / HD (DR,EC, SEC & IC)
Thanks for Your attention !
Special Thanks to
Organizers & Lecturers !