  We report the observation of emission spectra from Rb*He_n exciplexes in
solid 4He. Two different excitation channels were experimentally identified,
viz., exciplex formation via laser excitation to the atomic 5P3/2 and to the
5P1/2 levels. While the former channel was observed before in liquid helium, on
helium nanodroplets and in helium gas by different groups, the latter creation
mechanism occurs only in solid helium or in gaseous helium above 10 Kelvin. The
experimental results are compared to theoretical predictions based on the
extension of a model, used earlier by us for the description of Cs*He_n
exciplexes. We also report the first observation of fluorescence from atomic
rubidium in solid helium, and discuss striking differences between the
spectroscopic feature of Rb-He and Cs-He systems.
