  The interaction between medium-weight nuclei and a strong zeptosecond laser
pulse of MeV photons is investigated theoretically. Multiple absorption of
photons competes with nuclear equilibration. We investigate the sudden regime.
Here the rate of photon absorption is so strong that there is no time for the
nucleus to fully equilibrate after each photon absorption process. We follow
the temporal evolution of the system in terms of a set of rate equations. These
account for dipole absorption and induced dipole emission, equilibration
(modeled in terms of particle-hole states coupled by the residual nuclear
interaction), and neutron decay (populating a chain of proton-rich nuclei). Our
results are compared with earlier work addressing the adiabatic regime where
equilibration is instantaneous. We predict the degree of excitation and the
range of nuclei reached by neutron evaporation. These findings are relevant for
planning future experiments.
