International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 4.2, p. 193

Figure 4.2.1.2 

U. W. Arndta
[Figure 4.2.1.2]
Figure 4.2.1.2

Experimental measurements of [N_\varphi] for Cu K-L3 as functions of the accelerating voltage for different take-off angles. From Metchnik & Tomlin (1963[link]).