Environmental Engineering Reference
In-Depth Information
Ta b l e 4 . 15
The diffusion coefficient
D
0
of metal clusters in accordance with (4.110) reduced to
the normal number density of atoms. The diffusion coefficients are given in units of 10
3
cm
2
/s
and correspond to the gas temperature
T
D
600 K [91, 92].
Cluster, gas
He
Ne
Ar
Kr
Xe
H
2
N
2
Ti
0.84
0.52
0.68
0.58
0.60
1.8
0.89
Fe
0.95
0.59
0.77
0.65
0.68
2.1
1.0
Co
0.97
0.60
0.78
0.66
0.69
2.1
1.0
Ni
0.97
0.60
0.78
0.66
0.69
2.1
1.0
Cu
0.95
0.59
0.77
0.65
0.68
2.1
1.0
Zn
0.88
0.55
0.71
0.61
0.63
1.9
0.94
Sr
0.82
0.51
0.66
0.56
0.58
1.8
0.87
Mo
0.87
0.54
0.70
0.60
0.62
1.9
0.93
Pd
0.87
0.54
0.70
0.60
0.62
1.9
0.93
Ag
0.84
0.52
0.68
0.58
0.60
1.8
0.89
Ba
0.55
0.34
0.44
0.38
0.39
1.2
0.58
Ta
0.83
0.52
0.67
0.57
0.59
1.8
0.88
W
0.87
0.54
0.70
0.59
0.62
1.9
0.92
Re
0.88
0.55
0.71
0.61
0.63
1.9
0.94
Ir
0.88
0.54
0.71
0.60
0.63
1.9
0.93
Pt
0.89
0.55
0.72
0.61
0.64
1.9
0.94
Au
0.85
0.45
0.68
0.58
0.60
1.8
0.90
Tl
0.72
0.44
0.58
0.50
0.52
1.6
0.77
Pb
0.71
0.49
0.57
0.49
0.51
1.6
0.75
U
0.79
0.49
0.64
0.54
0.56
1.7
0.84
Pu
0.82
0.51
0.66
0.56
0.59
1.8
0.87
and clusters do not influence the distribution function for atoms. From this we
have for the force that acts on a moving cluster in the kinetic regime of its drift
Z
m
a
g
(1
σ
Z
m
a
λ
h
g
g
F
D
cos
#
)
'
(
v
)
gd
σ
d
v
D
m
g
'
(
v
)
gd
v
D
i
,
1
N
a
λ
D
,
(4.111)
σ
where
d
is the differential cross section of atom-cluster scattering, the diffusion
cross section
σ
r
0
and is given by (2.18), and
an average is made over the Maxwell distribution function for atoms.
Taking the cluster velocity
w
and force
F
acting on a cluster to be directed along
the
z
-axis, we assume
w
σ
of atom-cluster collision is
σ
D
π
v
and perform expansion over this small parameter.
