  Vibrationally resolved photoionization spectra of RbHe exciplexes forming on
He nanodroplets are recorded using femtosecond pump-probe spectroscopy with
amplitude-shaped probe pulses. The time-evolution of the spectra reveals an
exciplex formation time ~10ps followed by vibrational relaxation extending up
to >1ns. This points to an indirect, time-delayed desorption process of RbHe
off the He surface.
