The data file AMJUEL: Additional Atomic and Molecular ... - eirene

Types of Data, general prescriptions
H.0: interaction potentials
The classical elastic collision kinetics is determined by the interaction potential V (r). In
EIRENE for given (random sampling) impact parameter b and relative collision energy Er (in
eV) the deflection angle χ in the center of mass system is computed and the test particle velocity
is then changed accordingly in the laboratory system. There are various options for potential
functions V (r). The potential is always in eV, and the distance r (and also b in EIRENE) are in
(atomic) units of the Bohr radius a0 = 0.529 × 10 −8 cm. The parameter FIT-FLAG determines
which particular fit expression is used for the potential. The potential V (r) can be specified
then by up to 9 fit coefficients p0, . . . , p8, see Section 0.
FIT-FLAG=
=1 purely repulsive potential: to be written
=2 Morse like potential:
with
with the parameters:
p0 = ϵ (eV)
p1 = g1
p2 = g2
V (r) = ϵ [
e 2g(1−ρ) − 2e g(1−ρ)]
ρ := r/rm ; g :=
{ g1 for ρ < 1
g1g2 for ρ ≥ 1
p3 = rm (in units of a0), the minimum of V (r) : V (rm) = −ϵ
Derived Parameters ( are: )
ln 2
p4 = r0 = rm 1 − , the root of V (r) : V (r0) = 0
g1 ( )
p5 = rw = rm 1 + , the point of inflection of V (r)
p6 not in use
p7 = V (rw) = − 3ϵ
4
p8 not in use
ln 2
g1g2
H.1: cross section vs. energy
Fits for σ(Elab,1) [cm 2 ]
Collision cross are functions of relative velocity, but, due to historic reasons in the EIRENE
databases, which initially had been build on data of ref. [2], the laboratory energy of one of
the colliding particles (usually the charged particle) is used, with the second collision partner
(usually the neutral particle) being at rest. I.e., σ = σ(Elab,1). To convert to center of mass
energies, one uses Elab,1 = m1/2 v 2 1 and ECM = µ/2 v 2 rel with µ = m1m2/(m1 + m2) being
the reduced mass and vrel = |v1 − v2| the relative collision velocity
H.2: rate coefficients vs. temperature (zero beam energy)
Fits for ⟨σ · v⟩(Tp) [cm 3 /s]
25
(1)
(2)