  The refraction of space-time (ST) wave packets offers many fascinating
surprises with respect to conventional pulsed beams. In paper (I) of this
sequence, we described theoretically the refraction of all families of ST wave
packets at normal and oblique incidence at a planar interface between two
non-dispersive, homogeneous, isotropic dielectrics. Here, in paper (II) of this
sequence, we present experimental verification of the novel refractive
phenomena predicted for `baseband' ST wave packets upon normal incidence on a
planar interface. Specifically, we observe group-velocity invariance, normal
and anomalous refraction, and group-velocity inversion leading to group-delay
cancellation. These phenomena are verified in a set of optical materials with
refractive indices ranging from 1.38 to 1.76, including MgF$_2$, fused silica,
BK7 glass, and sapphire. We also provide a geometrical representation of the
physics associated with anomalous refraction in terms of the dynamics of the
spectral support domain for ST wave packets on the surface of the light-cone.
