Chapter/Index: Introduction | A |
B |
C |
D |
E |
F |
G |
H |
I |
J |
K |
L |
M |
N |
O |
P |
Q |
R |
S |
T |
U |
V |
W |
X |
Y |
Z |
Appendix
Angular/Polar Distribution of X-ray Generation in Electron Microscopy
Based on theoretical electrodynamics with the interaction of incident electrons on a surface, the angular distribution of generated X-rays can be give in the form of polar equation, [1]
----------------------- [1001]
where,
θ -- the angle between the directions of emission and acceleration.
-- the electron acceleration.
Equation 1001 results in a typical dipole characteristic:
i) a maximum of emission perpendicular at θ = 90° to the dipole.
ii) a zero emission parallel at θ = 0 and 180° to the dipole.
As shown in Figure 1001, the maximum emission of the x-ray continuum is shifted to smaller angles B because:
i) the Coulomb field of a moving charge is not exactly radially-symmetric owing to relativistic effects.
ii) a retardation has to be taken into account due to the finite velocity of wave propagation.
Figure 1001. Polar diagram of the angular distribution of the x-ray continuum generated in Al (left) and Au (right). [1] |
[1] Ludwig Reimer, Scanning Electron Microscopy: Physics of Image Formation and Microanalysis, 1998.
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