Chemistry Reference
In-Depth Information
TABLE1.5.Factors
k
ij
andShieldingConstants
σ
i
ofCharacteristicX-RayLines
andAbsorptionEdgesExperimentallyDeterminedforSeveralElementsAccording
toMoseley'sLaw
Quantum
Number
K
Edge
L
3
Edge
M
4
Edge
K
α
1
K
β
1
L
α
1
M
α
1
n
j
, initial
2
3
1
3
2
4
3
∞
2
∞
3
∞
n
i
, final
1
1
k
ij
[eV]
10.204
12.094
13.606
1.890
3.401
0.661
1.512
Atomic
Number
Z
σ
i
for
K
α
1
σ
i
for
K
β
1
σ
i
for K
Edge
σ
i
for
L
α
1
σ
i
for L
3
Edge
σ
i
for
M
α
1
σ
i
for M
4
Edge
6-10
0.83
11-15
0.93
1.64
2.11
16-20
0.97
1.73
2.52
21-25
0.97
1.80
2.85
26-30
0.93
1.87
3.14
6.73
12.14
31-35
0.86
1.87
3.38
6.95
13.26
36-40
0.74
1.84
3.56
7.08
14.17
41-45
0.57
1.76
3.66
7.19
14.94
46-50
0.34
1.61
3.69
7.28
15.67
51-55
1.48
3.67
7.34
16.37
21.35
32.93
56-60
7.39
17.08
21.46
33.92
61-65
7.40
17.76
21.65
35.28
66-70
7.39
18.43
21.85
36.87
71-75
7.35
19.07
22.08
38.31
76-80
7.31
19.67
22.29
39.67
81-85
7.25
20.20
22.47
40.86
86-90
7.20
20.64
22.61
41.85
91-95
22.68
42.39
For the K series with
n
i
=
1,
σ
i
takes experimental values of about 3; for the L
series with
n
i
=
2,
σ
i
values lie around 17; and for the M series with
n
i
=
3, these
values are around 39.
E
min
is also the minimum energy of photons, needed for
the excitation in X-ray fluorescence when a sample is irradiated by an X-ray
tube. And it gives the position of the absorption edges of the different K-, L-, or
M-shells (see Section 1.4.1). The respective characteristic peaks of the elements
always lie just below these edges.
Moseley's law is not very stringent since relative deviations of 0.1-0.2% for
the lines and of 0.5-2% for the edges occur. Consequently, the exact positions
of characteristic X-ray lines and respective edges are not calculated in practice
by using this law but instead are obtained from tables or computer memories
with measured values. They normally give the energies and wavelengths of the
peaks and additionally their relative intensities within the defined K, L, or M
series. The relative intensity of a certain peak in its series is determined by the
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