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MPINP:
Research group A. Pálffy – Division C. H. Keitel
Abstract:
Experimental developments in the field of petawatt lasers promise to provide in
the near future strong zeptosecond multi-MeV photon pulses. The interaction
of such pulses with nuclei would provide access to regimes so far unexplored
of high nuclear excitation energy and low angular momentum. In this thesis
we investigate theoretically for the first time the sudden regime of laser-nucleus
interaction, in which multiple photon absorption occurs faster than the nucleus
has time to equilibrate. We construct a master equation that determines the
temporal evolution of the nuclear state starting from the underlying processes:
dipole absorption, stimulated dipole emission, equilibration and neutron
evaporation. Equilibration is taken into account by considering the coupling
of states with different particle-hole numbers at constant energy. We use
state-of-the-art matrix exponential solvers based on the Chebyshov rational
approximation method to solve numerically the master equation. The results
show the interplay between photon absorption and nuclear equilibration
and its effects on neutron emission. Our quantitative estimates predict the
excitation path and range of nuclei reached by neutron decay towards the
proton-rich region of the nuclide table and provide relevant information for
the layout of future experiments.
