分类: 物理学 >> 核物理学 提交时间: 2024-03-01
摘要: The exploration of spin symmetry (SS) in nuclear physics has been instrumental in identifyingatomic nucleus structures. In this study, we solve the Dirac equation from the relativistic mean field (RMF)in complex momentum representation. We investigated SS and its breaking in single-particle resonant stateswithin deformed nuclei, with a focus on the illustrative nucleus 168Er. This was the initial discovery of a resonant spin doublet in a deformed nucleus, with the expectation of the SS approaching the continuum threshold.With increasing single-particle energy, the splitting of the resonant spin doublets widened significantly. This escalating splitting implies diminishing adherence to the SS, indicating a departure from the expected behavior asthe energy levels increase. We also analyzed the width of the resonant states, showing that lower orbital angularmomentum resonances possess shorter decay times and that SS is preserved within broad resonant doublets, asopposed to narrow resonant doublets. Comparing the radial density of the upper components for the bound-stateand resonant-state doublets, it becomes evident that while SS is well-preserved in the bound states, it deteriorates in the resonant states. The impact of nuclear deformation (β2) on SS was examined, demonstrating that anincrease in β2 resulted in higher energy and width splitting in the resonant spin doublets, which is attributed toincreased component mixing. Furthermore, the sensitivity of spin doublets to various potential parameters suchas surface diffuseness (a), radius (R), and depth (Σ0) is discussed, emphasizing the role of these parametersin SS. This study provides valuable insights into the behavior of spin doublets in deformed nuclei and theirinterplay with the nuclear structure, thereby advancing our understanding of SS in the resonance state.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Focusing electromagnetic field to enhance the interaction with matter has been promoting researches and applications of nano electronics and photonics. Usually, the evanescent-wave coupling is adopted in various nano structures and materials to confine the electromagnetic field into a subwavelength space. Here, based on the direct coupling with confined electron oscillations in a nanowire, we demonstrate an extreme localization of microwave field down to 10$^{-6}\lambda$. A hybrid nanowire-bowtie antenna is further designed to focus the free-space microwave to this deep-subwavelength space. Detected by the nitrogen vacancy center in diamond, the field intensity and microwave-spin interaction strength are enhanced by 2.0$\times$10$^{8}$ and 1.4$\times$10$^{4}$ times, respectively. Such an extreme concentration of microwave field will further promote integrated quantum information processing, sensing and microwave photonics in a nanoscale system.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: High-energy ultraviolet pulse generation in gas-filled hollow capillary fibers (HCFs) through dispersive-wave-emission process, has attracted considerable attentions in recent several years due to its great application potentials in ultraviolet spectroscopy and photochemistry. While the ability of this technique to deliver high-energy, ultrafast ultraviolet pulses is widely recognized, few-fs duration of {\mu}J-level dispersive-wave (DW) pulses has, however, escaped direct measurements. In this letter, we demonstrate that using several chirped mirrors, few-fs ultraviolet DW pulses can be obtained in atmosphere environment without the use of vacuum chambers. The pulse temporal profiles, measured using a self-diffraction frequency-resolved optical gating set-up, exhibit full-width-half-maximum pulse widths of 9.6 fs at 384 nm and 9.4 fs at 430 nm, close to the Fourier-transform limits. Moreover, theoretical and experimental studies reveal the strong influences of driving pulse energy and HCF length on temporal width and shape of the measured DW pulses. The ultraviolet pulses obtained in atmosphere environment with {\mu}J-level pulse energy, few-fs pulse width and broadband wavelength tunability are ready to be used in many applications.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: We demonstrate the stable and flexible light delivery of multi-{\mu}J, sub-200-fs pulses over a ~10-m-long vacuumized anti-resonant hollow-core fiber (AR-HCF), which was successfully used for high-performance pulse synchronization. Compared with the pulse train launched into the AR-HCF, the transmitted pulse train out of the fiber exhibits excellent stabilities in pulse power and spectrum, with pointing stability largely improved. The walk-off between the fiber-delivery and the other free-space-propagation pulse trains, in an open loop, was measured to be <6 fs root-mean-square (RMS) over 90 minutes, corresponding to a relative optical-path variation of <2x10-7. This walk-off can be further suppressed to ~2 fs RMS simply using an active control loop, highlighting the great application potentials of this AR-HCF set-up in large-scale laser and accelerator facilities.