Scanning Electron Microscopy and X-Ray Microanalysis

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4.2.4 X-Ray Nomenclature

Two systems are in use for designating X-rays. The
traditional but now archaic Siegbahn system lists the
shell where the original ionization occurs followed by a
Greek letter or other symbol that suggests the order of
the family members by their relative intensity, α > β > γ

η > ζ. For closely related members, numbers are also
attached, for example, Lβ 1 through Lβ 15. Additionally,
Latin letters are used for the complex minor L-shell fam-
ily members: l, s, t, u, and v. While still the predominant
labeling system used in commercial X-ray microanalysis
software systems, the Siegbahn system has been officially

replaced by the International Union of Pure and Applied

Chemistry (IUPAC) labeling protocol in which the first

term denotes the shell or subshell where the original ion-

ization occurs while the second term indicates the sub-

shell from which the electron transition occurs to fill the

vacancy; for example, Kα 1 is replaced by K-L 3 for a K-shell

ionization filled from the L 3 subshell.. Table 4.1 gives

the correspondence between the Siegbahn and IUPAC

labeling schemes for the characteristic X-rays likely to

be detected by energy dispersive X-ray spectrometry.

Note that for the M-shell, there are minor family mem-

bers detectable by EDS for which there are no Siegbahn

designations.

K

L 2

L 1

K

L 1

L 2

L 3

M 5

M 4

M 3

M 2

M 1

Ka 1

N 7

N 6

N 5

N 4

N 3

N 2

N 1

Kb 1

K-L 2

K-L 3

K-M 3

K-N 3

Ka 2

Kb 2

a

b

K

L 1

L 2

L 3

M 5

M 4

M 3

M 2

M 1

L 3 - M 5

c

La 1

N 7

N 6

N 5

N 4

N 3

N 2

N 1

L 2 - M 4

Lb 1 L 3 - M 1

LL (^3) a-M (^4) Ll
2
L 3 - N 5
Lb 2 L^1 - M^3
Lb 3
L 1 - M 2
Lb 4
L 2 - N 4
Lg 1 L 1 - N 2
Lg 2 LL^1 g-N^3
3
L 2 - M 1
Lh
N 7
N 6
N 5
N 4
N 3
N 2
N 1
M 5
M 4
M 3
M 2
M 1
L 3
L 2
L 1
K
M 5 - N 7
d
M 5 - N 6 M 4 - N 6 M 3 - N 5 M4,5-N2,3
Mα 1 Mα 2 Mβ Mγ Mζ

. Fig. 4.4 a Atomic shell energy level diagram for carbon illustrating
the permitted shell transition K–L 2 (shown in green) and the forbidden
transition K–L 1 (shown in red). b Atomic shell energy level diagram
illustrating possible K-shell vacancy-filling transitions. c Atomic shell

energy level diagram illustrating possible L-shell vacancy-filling transi-

tions. d Atomic shell energy level diagram illustrating some possible

M-shell vacancy-filling transitions

4.2 · Characteristic X-Rays