48
4
direction of the electron travel. In thin specimens where the
beam electron trajectories are nearly aligned, this anisotropy
can result in a different continuum intensity in the forward
direction along the beam relative to the backward direction.
However, in thick specimens, the near-randomization of
the beam electron trajectory segments by elastic scattering
effectively smooths out this anisotropy, so that the X-ray con-
tinuum is effectively rendered isotropic.
0246810
Overvoltage, U = E 0 /Ec
Relative X-ray intensity (thick specimen)
50
40
30
20
10
0
Relati
ve
X-
ray intensit
y
. Fig. 4.9 Characteristic X-ray inten-
sity emitted from a thick specimen;
exponent n = 1.7
Eν=E 0
Eν
. Fig. 4.10 Schematic illustration of
the braking radiation (bremsstrahlung)
process giving rise to the X-ray
continuum
Chapter 4 · X-Rays