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MPINP:
Research group A. Pálffy – Division C. H. Keitel
Abstract:
In the course of this Thesis the mutual control between x-rays and nuclear transitions is
investigated theoretically. In the first Part, we study the nuclear photoexcitation with
the highly brilliant and coherent x-ray free-electron lasers (XFELs). Apart from amplifying
the direct resonant interaction with nuclear transitions, the super-intense XFEL
can produce new states of matter like cold, high-density plasmas where secondary nuclear
excitation channels may come into play, e.g., nuclear excitation by electron capture
(NEEC). Our results predict that in the case of 57Fe targets secondary NEEC can be
safely neglected, whereas it is surprisingly the dominating contribution (in comparison
to the direct photoexcitation) for the XFEL-induced 93mMo isomer triggering. Based
on these case studies, we elaborate a general set of criteria to identify the prevailing
excitation channel for a certain nuclear isotope. These criteria may be most relevant
for future nuclear resonance experiments at XFEL facilities. On the opposite frontier,
the interplay between single x-ray photons and nuclear transitions offer potential storage
and processing applications for information science in their most compact form. In
the second Part of this Thesis, we show that nuclear forward scattering off 57Fe targets
can be employed to process polarization-encoded single x-rays via timed magnetic field
rotations. Apart from the realization of logical gates with x-rays, the polarization encoding
is used to design an x-ray quantum eraser scheme where the interference between
scattering paths can be switched off and on in a controlled manner. Such setups may
advance time-energy complementarity tests to so far unexplored paramater regimes, e.g.,
to the domain of x-ray quanta.
