arXiv subjects

Zuoye Liu

Publications and source records attributed to Zuoye Liu.

8 recordsLinked to original sources

arXiv2026

Nuclear non-resonant photoexcitation assisted by electron recombination

We investigate theoretically a nuclear excitation mechanism involving absorption of non-resonant photons leveraged by the coupling to the atomic shell. The nuclear non-resonant photoexcitation is assisted by electron recombination which compensates the energy mismatch between photon and nuclear transition energies, reminiscent of parametric up-conversion in non-linear media. This third-order process proceeds via a virtual nuclear state rather than virtual electronic states, distinguishing this mechanism from the electronic bridge. We investigate the process on the example of a so-far not observed 14.2 keV hard x-ray transition in 193Pt driven by an x-ray free-electron laser. Although the calculated cross section is small, it can be compensated by the vast number of non-resonant photons from the x-ray laser pulse. By enabling nuclear excitation through non-resonant photons, this up-conversion-like mechanism suggests new directions for non-linear x-ray interactions mediated by nuclear transitions.

nucl-th↗

arXiv2025

Probing Nuclear Excitation by Electron Capture in an Electron Beam Ion Trap with Non-destructive Isomer Detection via Precision Mass Spectrometry

Nuclear excitation by electron capture (NEEC) is an important nuclear excitation mechanism which still lacks conclusive experimental verification. This is primarily attributed to strong background x-/$\gamma$-ray noise and competing nuclear excitation processes which would overshadow the signals in various environments that NEEC takes place. Here, we propose an experimental approach to observe the NEEC process within a background-free environment. Through collisions with a highly-compressed mono-energetic electron beam in an electron beam ion trap, nuclei may get excited to a long-lived isomeric state via the NEEC process. Subsequently, ions can be extracted and Penning-trap mass spectrometry employed to unambiguously detect the isomer. Our study focuses on the promising candidate $^{189}\mathrm{Os}$, demonstrating measurable detection rates of the NEEC process and discussing the feasibility of the proposed approach. This new approach for observing the NEEC process may be realized in the near future.

nucl-ex↗

arXiv2024

Beam Pointing of Relativistic High-order Harmonics Genrated on a Nonuniform Pre-plasma

The use of tunable pre-pulse is a common technique to enhance the high-order harmonic generation from surface plasma. The shape and dynamic of the electron density, the degree of ionization and its rate, and the plasma heating are influenced by the pre-pulse properties. Non-uniform pre-pulse could cause a spatially varying density map to the pre-plasma region, which serves as the spectrally up-conversion and reflection surface. The corresponding geometrical feature and plasma nature under laser field will affect the harmonic emission properties. In this study, the variation in harmonic beam pointing due to the electron density shape was investigated. Particle-in-cell simulations demonstrated that both plasma hydrodynamics and geometrical optical effect induce the deviation of harmonic beam from specular reflection. This research contributes to the understanding of the surface plasma dynamics during high harmonic generation process.

physics.plasm-ph↗

arXiv2022

The clamped intensity of femtosecond laser pulses varying with gas pressure in the presence of external focusing

We perform a theoretical investigation of the clamped laser intensity inside the filament plasma as a function of gas pressure with external focusing. Unlike the clamped intensity under the selffocusing condition, which is independent on the gas pressure, the clamped intensity with external focusing decreases with the gas pressure. Our findings can explain the changes of the signals of femtosecond-laser-induced 391-nm forward emission and fluorescence with the nitrogen gas pressure.

physics.plasm-ph↗

arXiv2022

Storage and manipulation of single x-ray photons via nuclear hyperfine splitting

We introduce a technique to store and manipulate single x-ray photons which relies on dynamically controlled absorption via nuclear hyperfine magnetic splitting. This scheme is inherently suitable for storage, on-demand generation and dynamical manipulation of single x-ray photons, for instance, the manipulation of the temporal shape, temporal splitting, the interference between x-ray photons and the control of the polarization. Our approach opens up new paths in x-ray quantum information.

quant-ph↗

arXiv2018

Ultrafast dynamic evolution of multilevel systems in medium-strength laser fields

The ultrafast dynamic evolution of an atomic system under medium-strength laser fields is studied by performing transient absorption measurement. An analytical model developed from perturbation theory with a modified transition dipole moment is presented to explain the spectral features of the multilevel system. By fitting the measured absorption spectra to the model, the system's dynamic evolution is quantified by different amplitude and phase modulation factors in the pump--probe and probe--pump scenarios. This study provides a way to understand laser--matter interaction in the transition area between the strong-field and weak-field regimes.

physics.atom-ph↗

arXiv2013

Generation of high-frequency combs locked to atomic resonances by quantum phase modulation

A general mechanism for the generation of frequency combs referenced to atomic resonances is put forward. The mechanism is based on the periodic phase control of a quantum system's dipole response. We develop an analytic description of the comb spectral structure, depending on both the atomic and the phase-control properties. We further suggest an experimental implementation of our scheme: Generating a frequency comb in the soft-x-ray spectral region, which can be realized with currently available techniques and radiation sources. The universality of this mechanism allows the generalization of frequency-comb technology to arbitrary frequencies, including the hard-x-ray regime by using reference transitions in highly charged ions.

physics.atom-ph↗

arXiv2013

Elongation of energy exchange between femtosecond laser pulses via plasma formation in air

We experimentally demonstrate energy exchange between a delay-tuned femtosecond beam and two delay-fixed ones as they spatiotemporally overlapped and experienced filamentation in air. The energy exchange process in the relative time delay is dramatically elongated up to 40 ps in the presence of plasma grating, indicating that filamentary beams coupling may be an effective method for filament control.

physics.optics↗