Environmental Engineering Reference
In-Depth Information
Ta b l e 2 . 22
Radiative parameters and the absorption coefficient for the spectral line center for
resonant radiative transitions in atoms of the first and second groups of the periodic table [8,
146].
v
σ
t
,10
7
cm
3
/s
k
0
,10
5
cm
1
Element
Transition
λ
,nm
τ
,ns
g
/
g
0
1
2
S
2
2
P
H
!
121.57
1.60
3
0.516
8.6
1
1
S
2
1
P
He
!
58.433
0.56
3
0.164
18
2
2
S
3
2
P
Li
!
670.8
27
3
5.1
1.6
2
1
S
2
1
P
Be
!
234.86
1.9
3
9.6
1.4
3
2
S
1/2
!
3
2
P
1/2
Na
589.59
16
1
3.1
1.1
3
2
S
1/2
!
3
2
P
3/2
Na
589.0
16
2
4.8
1.4
3
1
S
3
1
P
Mg
!
285.21
2.1
3
5.5
3.4
4
2
S
1/2
!
4
2
P
1/2
K
769.0
27
1
4.1
0.85
4
2
S
1/2
!
4
2
P
3/2
K
766.49
27
2
6.3
1.1
4
1
S
4
1
P
Ca
!
422.67
4.6
3
7.3
2.5
4
2
S
1/2
!
4
2
P
1/2
Cu
327.40
7.0
1
1.1
2.1
4
2
S
1/2
!
4
2
P
3/2
Cu
324.75
7.2
2
1.7
2.8
4
1
S
4
1
P
Zn
!
213.86
1.4
3
3.3
4.8
5
2
S
1/2
!
5
2
P
1/2
Rb
794.76
28
1
3.9
0.91
5
2
S
1/2
!
5
2
P
3/2
Rb
780.03
26
2
6.2
1.2
5
1
S
5
1
P
Sr
!
460.73
6.2
3
9.4
1.7
5
2
S
1/2
!
5
2
P
1/2
Ag
338.29
7.9
1
1.1
2.0
5
2
S
1/2
!
5
2
P
3/2
Ag
328.07
6.7
2
1.7
2.9
5
1
S
5
1
P
Cd
!
228.80
1.7
3
3.3
4.5
6
2
S
1/2
!
6
2
P
1/2
Cs
894.35
31
1
5.3
0.77
6
2
S
1/2
!
6
2
P
3/2
Cs
852.11
27
2
8.1
1.0
6
1
S
6
1
P
Ba
!
553.55
8.5
3
9.0
1.9
6
2
S
1/2
!
6
2
P
1/2
Au
267.60
6.0
1
0.49
1.9
6
2
S
1/2
!
6
2
P
3/2
Au
242.80
4.6
2
0.75
4.2
6
1
S
6
1
P
Hg
!
184.95
1.3
3
2.2
5.7
Note that in the case under consideration, broadening of a spectral line is deter-
mined by atomic collisions and corresponds to the criterion
N
0
d
2
„
ω
c
,
(2.150)
where
T
,which
allows us to ignore stimulated radiation processes. Using (2.145) for the absorption
cross section, we have for the absorption coefficient (2.149) in the spectral line
center
is a typical velocity of atoms. In addition, we assume
„
ω
v
c
2
ω
a
0
τ
k
0
D
N
0
σ
ω
N
0
.
2
r
