## Tyndall effect was observed using a xA nm YAG green

In summary, the photoelectron signal intensity may be considerably affected by the use of the dipole approximation in the theoretical models describing the photoelectron transport. For photoelectron kinetic energies of 10 keV, the deviation due to the use of the first correction for nondipolar effects (NDA1) may reach 40%. Further improvement of accuracy due to the use of the second correction (NDA2) is much less pronounced. At 10 keV, the difference between photoelectron intensities calculated from the NDA1 and NDA2 theoretical models does not exceed 6%, and it PF00562271 is still smaller at lower photoelectron energies. In contrast, parameters describing the photoelectron transport, mean escape depth and the attenuation length, practically do not depend on the photoemission cross section in wide range of experimental configurations, i.e. for emission angles up to 50° with respect to the surface normal. This conclusion may of importance in the practical HAXPES applications because the algorithms for calculating the EAL and MED, derived for XPS based on the Mg Kα and Al Kα sources, seem to be valid for high energy sources. The only one parameter, the asymmetry parameter β, is then needed to define the photoemission cross section. An attempt has been made to identify reasons for stability of EALs and MEDs. The observed insensitivity to accuracy of the photoemission cross section has been tentatively ascribed to experimental configurations in which the relevant emission depth distribution function (EMDDF) is close to exponential. If additionally, variation of the photoemission cross section does not change the slope of the EMDDF in semi-logarithmic coordinates, one can prove that the considered parameters do not depend on the shape of the photoemission cross section. This explanation also seems to apply to photoelectrons emitted by the polarized X-rays. This issue will be approached in a separate study.