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

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 !!!

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 !!!

Quasi-diabatic Representationof relevant molecular states

AB**

AB*

AB+

A + B*

A + B+

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 !!!

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

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

MQDT vs ExperimentsHD+ / 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=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

MQDT vs ExperimentsHD+ / 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

Indirect process

&

Rotationnal effects

Direct process !

Rotationnal effects neglected

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

Indirect process

&

Rotationnal effects

thin ≡HD+/HD

bold ≡ DT+/DT

Boundary of the fusion plasma (IV) HD+ / HD (DR,EC, SEC & IC)

Thanks for Your attention !

Special Thanks to Organizers & Lecturers !