Approaches to resonant tabletop nuclear isomer excitation

By looking at the optical photons and x-rays emitted by atoms we learned much about atomic structure and by looking at gamma spectra we learned about nuclear structure. We started to listen to the world around us by looking at photons. With the advent of laser spectroscopy, we started talking back using photons. Recently, nuclear spectroscopy is following the same path. When talking to nuclei by using photons we notice that strangely the nucleus prefers to talk to surrounding electrons. This is seen as a nuisance so the electron-nucleus communication is silenced. Using photons, strong x-ray sources are needed to see a response from the nucleus, which can only be produced in large facilities (free electron lasers, synchrotrons). It seems that electrons and photons like to talk, and nuclei and electrons, but not photons and nuclei. To improve the communication between photons, electrons and nuclei I proposed a new research direction, with the help of the FWF Schrödinger program. Through hard work and intercommunication of many researchers, some points became clear: We can get photons to talk to electrons, and if we get electrons to talk to nuclei it should become much easier to have a spectroscopic conversation! As expected, when the electron energies are the same as the nuclear energies, the interaction increases. It was calculated that processes such as nuclear Electron Bridge (EB) excitation through defects, Nuclear Excitation by Electron Capture (NEEC) and by Electron Transition (NEET) would resonantly enhance the probability of nuclear excitation and subsequent spectroscopy. A stronger interaction with nuclei means we can miniaturize nuclear spectroscopy and expand the discussion with nuclei out from large facilities into smaller laboratories. To study EB, we look at electrons in crystalline CaF2 and thorium-229 nuclei doped in this material. By doping thorium into CaF2, imperfections are created that are new electronic states in the vicinity of the thorium nucleus. By exciting these electrons, we should be able to increase nuclear excitation rates by a factor of a hundred. We study NEET/NEEC by shooting high energy electrons at gold which kick out the inner electrons of gold. The leftover hole can be filled by an outer electron and either emit an x-ray or excite the nucleus. Since the energy of this process is almost perfectly resonant, by chance, with a nuclear excitation we can manipulate the electron-nucleus interaction by finely tuning the involved energies. This research attempts to build the tools to easily talk to nuclei, in the hope that this conversation leads to many new insights!