  Direct evidence of excitation of the 5p3/2 -> 6p3/2 electric dipole forbidden
transition in atomic rubidium is presented. The experiments were performed in a
room temperature rubidium cell with continuous wave extended cavity diode
lasers. Optical-optical double resonance spectroscopy with counterpropagating
beams allows the detection of the non-dipole transition free of Doppler
broadening. The 5p3/2 state is prepared by excitation with a laser locked to
the maximum F cyclic transition of the D2 line, and the forbidden transition is
produced by excitation with a 911 nm laser. Production of the forbidden
transition is monitored by detection of the 420 nm fluorescence that results
from decay of the 6p3/2 state. Spectra with three narrow lines (~ 13 MHz FWHM)
with the characteristic F - 1, F and F + 1 splitting of the 6p3/2 hyperfine
structure in both rubidium isotopes were obtained. The results are in very good
agreement with a direct calculation that takes into account the 5s -> 5p3/2
preparation dynamics, the 5p3/2 -> 6p3/2 non-dipole excitation geometry and the
6p3/2 -> 5s1/2 decay. The comparison also shows that the electric dipole
forbidden transition is a very sensitive probe of the preparation dynamics.
