  Energy absorption of xenon clusters embedded in helium nanodroplets from
strong femtosecond laser pulses is studied theoretically. Compared to pure
clusters we find earlier and more efficient energy absorption in agreement with
experiments. This effect is due to resonant absorption of the helium nanoplasma
whose formation is catalyzed by the xenon core. For very short double pulses
with variable delay both plasma resonances, due to the helium shell and the
xenon core, are identified and the experimental conditions are given which
should allow for a simultaneous observation of both of them.
