  On speed of a photon in a dispersing medium Ogluzdin Valeriy E. Abstract
Based on the author of the experimental results and their treatment, a model
that demonstrates that the real dispersive medium in spectral regions where the
refractive index greater than unity, the velocity of propagation of photons in
this environment corresponds to the phase velocity of light. These portions of
the spectrum (for example, atomic potassium vapor or other alkali metal) are
from low-frequency side of the main lines of the doublet and are available for
research using tunable lasers. In the calculations took into account the fact
that the atomic vapor of alkali metal used as a dispersing medium, in
accordance with the theory of dispersion in the above sections of the spectrum,
on the periphery of the cross section of laser beam with Gaussian intensity
distribution across the beam - in the shadows refractive index n ({\nu}) is
greater than unity, and the axis of the beam, where the radiation intensity is
maximum - for radiation following the leading edge of the light pulse, the
refractive index is unity, which ensures smooth on the beam axis, without any
delay "superluminal "propagation of light with velocity c. This fact causes the
appearance of the shadow cone of Vavilov - Cherenkov radiation, indicating a
slow propagation of photons from the source of the cone with phase velocity c /
n ({\nu}).
