The new regime of resonant nuclear photoexcitation rendered possible by x-ray free electron laser beams interacting with solid state targets is investigated theoretically. Our results unexpectedly show that secondary processes coupling nuclei to the atomic shell in the created cold high-density plasma can dominate direct photoexcitation. As an example we discuss the case of 93m Mo isomer depletion for which nuclear excitation by electron capture as secondary process is shown to be orders of magnitude more efficient than the direct laser-nucleus interaction. General arguments revisiting the role of the x-ray free electron laser in nuclear experiments involving solid-state targets are further deduced. The new X-ray Free Electron Laser (XFEL) facilities [1, 2] may provide both the x-ray photon energies and the very high brilliance required for resonant driving of nuclear transitions [3][4][5][6][7][8][9][10]. So far, the resonant interaction between nuclei and the electromagnetic field was studied in experiments performed with broadband synchrotron radiation (SR) [11] or bremsstrahlung [12]. The peak brilliance of XFEL light reaches up to eight orders of magnitude higher than that of SR sources [13] and is expected to bring significant progress in light-nucleus interaction experiments. In particular SR experiments with Mössbauer solid-state targets, mostly involving 57 Fe [14-16], provide only weak nuclear excitation despite the high target density and could benefit from the XFEL intensity. While so far in these experiments the electronic response only acted as background, the increase of the electric field strength leads to drastic changes in the interaction between photons and electrons which may additionally influence the nuclear excitation. Due to the unique interaction between high intensity x-ray pulses and matter [17,18] new states like cold, high-density plasmas can originate [19,20]. In such environments secondary nuclear processes from the coupling to the atomic shell are rendered possible by the presence of free electrons and atomic vacancies. This is also a new and diametrically opposed situation compared to photonuclear studies involving petawatt optical lasers [21][22][23][24][25].In this Letter we investigate the nuclear excitation induced by the XFEL pulse shining on a nuclear solid-state target. We show that surprisingly, secondary nuclear excitation by electron capture (NEEC) in the occurring plasma can exceed by orders of magnitude the direct resonant photoexcitation despite the laser photons being tuned on the nuclear transition. Furthermore, we find that NEEC is more robust since it is less sensitive to the laser photon frequency fulfilling the resonance condition. This is a new feature as electronic processes were not relevant for experiments performed with SR, where the fast electronic response of the sample was negotiated by time gating [26,27]. The concrete example studied here is the case of photoexcitation starting from the 6.85 h long-lived isomeric state of 93 Mo at approx. 2.5 MeV exci...
The process of nuclear excitation by electron capture in plasma environments generated by the interaction of ultrastrong optical lasers with solid-state samples is investigated theoretically. With the help of a plasma model, we perform a comprehensive study of the optimal parameters for the most efficient nuclear excitation and determine the corresponding laser setup requirements. We discern between the low-density plasma regime, modeled by scaling laws, and the high-density regime, for which we perform particle-in-cell calculations. As a nuclear transition case study we consider the 4.85-keV nuclear excitation starting from the long-lived ^{93m}Mo isomer. Our results show that the optimal plasma and laser parameters are sensitive to the chosen observable and that measurable rates of nuclear excitation and isomer depletion of ^{93m}Mo should be already achievable at laser facilities existing today.
The optimal parameters for nuclear excitation by electron capture in plasma environments generated by the interaction of ultra-strong optical lasers with solid matter are investigated theoretically. As a case study we consider a 4.85 keV nuclear transition starting from the long-lived 93m Mo isomer that can lead to the release of the stored 2.4 MeV excitation energy. We find that due to the complex plasma dynamics, the nuclear excitation rate and the actual number of excited nuclei do not reach their maximum at the same laser parameters. The nuclear excitation achievable with a high-power optical laser is up to twelve and up to six orders of magnitude larger than the values predicted for direct resonant and secondary plasma-mediated excitation at the x-ray free electron laser, respectively. Our results show that the experimental observation of the nuclear excitation of 93m Mo and the subsequent release of stored energy should be possible at laser facilities available today.Novel coherent light sources open unprecedented possibilities for the field of laser-matter interactions [1]. The X-ray Free Electron Laser (XFEL) [2,3] for instance can drive low-energy electromagnetic transitions in nuclei. Ultra-strong optical laser systems with up to few petawatt power [4][5][6][7][8] are very efficient in generating plasma environments [9], which host complex interactions between photons, electrons, ions and the atomic nucleus. Nuclear excitation in laser-generated hot plasmas involving optical lasers [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], or cold high-density plasmas [27] at the XFEL [28,29] have been under investigation. Special attention has been attracted by nuclear transitions starting from long-lived excited states. Such states are also known as nuclear isomers and are particularly interesting due to their potential to store large amounts of energy over long periods of time [30][31][32][33][34][35][36][37]. A typical example is 93m Mo at 2.4 MeV, for which an additional excitation of only 4.85 keV could lead to the depletion of the isomer and release on demand of the stored energy.For both optical-and x-ray laser-generated plasmas, the process of nuclear excitation by electron capture (NEEC) [38,39] into the atomic shell has proven to have a significant contribution. As secondary process in the cold plasma environment generated by the interaction of the XFEL with solid-state targets, NEEC can exceed the direct nuclear photoexcitation by six orders of magnitude [28,29] for the 4.85 keV excitation starting from the 93m Mo isomeric state. In this Letter, we show that by tailoring optical-laser-generated plasmas to harness maximum nuclear excitation via NEEC, a further six orders of magnitude increase in the nuclear excitation and subsequent isomer depletion compared to the case of cold XFEL-generated plasmas can be reached. As an interesting point, we find that due to the complexity of the processes involved, the plasma and correspondingly laser parameters for reaching the maximal NEEC ra...
The direct and secondary nuclear excitation produced by an x-ray free electron laser when interacting with a solid-state nuclear target is investigated theoretically. When driven at the resonance energy, the x-ray free electron laser can produce direct photoexcitation. However, the dominant process in that interaction is the photoelectric effect producing a cold and very dense plasma in which also secondary processes such as nuclear excitation by electron capture may occur. We develop a realistic theoretical model to quantify the temporal dynamics of the plasma and the magnitude of the secondary excitation therein. Numerical results show that depending on the nuclear transition energy and the temperature and charge states reached in the plasma, secondary nuclear excitation by electron capture may dominate the direct photoexcitation by several orders of magnitude, as it is the case for the 4.8 keV transition from the isomeric state of $^{93}$Mo, or it can be negligible, as it is the case for the 14.4 keV M\"ossbauer transition in $^{57}\mathrm{Fe}$. These findings are most relevant for future nuclear quantum optics experiments at x-ray free electron laser facilities
Photonic qubits lie at the heart of quantum information technology, often encoding information in their polarization state. So far, only low-frequency optical and infrared photons have been employed as flying qubits, as the resources that are at present easiest to control. With their essentially different way of interacting with matter, x-ray qubits would bear however relevant advantages: they are extremely robust, penetrate deep through materials, and can be focused down to few-nm waveguides, allowing unprecedented miniaturization. Also, x-rays are resonant to nuclear transitions, which are very well isolated from the environment and present long coherence times. Here, we show theoretically that x-ray polarization qubits can be dynamically controlled by nuclear Mössbauer resonances. The control knob is played by nuclear hyperfine magnetic fields, that allow via fast rotations precise processing of single x-ray quanta polarization. With such rotations, single-qubit and binary logical operations such as a destructive C-NOT gate can be implemented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.