Accepted Papers
Recent catalogue
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Vol.74 No.3
2025-02-05
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Vol.74 No.2
2025-01-20
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Vol.74 No.1
2025-01-05
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Vol.73 No.24
2024-12-20
- All Archive
GENERAL
2025, 74 (3): 030701.
doi: 10.7498/aps.74.20241538
Abstract +
NUCLEAR PHYSICS
2025, 74 (3): 032101.
doi: 10.7498/aps.74.20240991
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This work mainly investigates the properties of the low-energy quadrupole strength in Ni isotopes, especially the evolution of the pygmy quadrupole states with the increase of neutron number. And the effect of shell evolution on the pygmy resonance is also discussed in detail. Based on the Skyrme Hartree-Fock+Bardeen-Cooper-Schrieffer (HF+BCS) theory and the self-consistent quasiparticle random phase approximation (RPA) method, the evolution in the nickel isotope chain with the increase of neutron number is studied. And in the calculations, three effective Skyrme interactions, namely SGII, SLy5 and SKM*, and a density-dependent zero-range type force are adopted. The properties of the first 2+ state in Ni isotopes are studied. A good description on the experimental excited energies of the first 2+ states are achieved, and the SGII and SLy5 can well describe the reduced electric transition probabilities for $^{58-68}{\rm{Ni}}$. It is found that the energy value of the first 2+ state for $^{68}{\rm{Ni}}$ and $^{78}{\rm{Ni}}$ are obviously high than those of other nuclei, reflecting the obvious shell effect. In addition to the first 2+ states, pygmy quadrupole states between 3 MeV and 5 MeV with relatively large electric transition probabilities are evidently found for $^{70-76}{\rm{Ni}}$ in the isoscalar quadruple strength distribution. The pygmy quadrupole states have the energy values decreasing with the number of neutrons increasing, but their strengths increase gradually. Therefore, they are more sensitive to the change in the shell structure. This is due to the fact that the gradual filling of the neutron level $1{{\mathrm{g}}}_{9/2}$ has a significant effect on the pygmy quadrupole states of $^{70-76}{\rm{Ni}}$, and it leads to switching from proton-dominated excitations to neutron-dominated ones. The pygmy quadrupole states for $^{70-76}{\rm{Ni}}$ are sensitive to the proton and neutron shell gaps, so they can provide the information about the shell evolution in neutron-rich nuclei.
DATA PAPER
2025, 74 (3): 033101.
doi: 10.7498/aps.74.20241461
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Reasonably designing high-capacity novel electrode materials is key to further enhancing the energy density of ion batteries. Graphene has been considered one of the most promising candidates for anodes in ion batteries. However, the weak interaction between pure graphene and the corresponding ions results in a low theoretical capacity. Based on this, in this work the first-principles calculation is used to assess the viability of two-dimensional Cu/NO2G, a single-atom copper-doped graphene anchored by nitrogen and oxygen, as an anode material for Li/Na/K-ion batteries. The results show that Cu/NO2G is stable in terms of thermodynamics and kinetics. It maintains good conductivity before and after the adsorption of Li/Na/K, with theoretical capacities of 1639.9 mAh/g for lithium, 2025.8 mAh/g for sodium, and 1157.6 mAh/g for potassium. In the embedding process of Li/Na/K, the lattice constant changes minimally (less than 1%), indicating excellent cycling stability. Additionally, the migration energy barriers for Li, Na, and K on the surface of Cu/NO2G are 0.339 eV, 0.209 eV, and 0.098 eV, respectively, demonstrating its superior rate performance. In summary, these results provide a solid theoretical foundation for rationally designing metal single-atom doped graphene as a novel anode material for alkali metal ion batteries. All the data presented in this paper are openly available at https://doi.org/10.57760/sciencedb.j00213.00063 .
SPECIAL TOPIC—Dynamics of atoms and molecules at extremes
2025, 74 (3): 033201.
doi: 10.7498/aps.74.20241321
Abstract +
The laser-produced Sn plasma light source is a critical component in advanced extreme ultraviolet (EUV) lithography. The power and stability of EUV radiation within a 2% bandwidth centered at 13.5 nm are key indicators that determine success of the entire lithography process .The plasma state parameter distributions and the EUV radiation spectrum for a laser-produced Sn plasma light source are numerically simulated in this work. The radiative opacity of Sn plasma within the 12–16 nm range is calculated using a detailed-level-accounting model in the local thermodynamic equilibrium approximation. Next, the temperature distribution and the electron density distribution of plasma generated by nanosecond laser pulses interacting with both a Sn planar solid target and a liquid droplet target are simulated using the radiation hydrodynamics code for laser-produced plasma, RHDLPP. By combining the radiative opacity data with the plasma state data, the spectral simulation subroutine SpeIma3D is employed to model the spatially resolved EUV spectra for the planar target plasma and the angle-resolved EUV spectra for the droplet target plasma at a 60-degree observation angle. The variation of in-band radiation intensity at 13.5 nm within the 2% bandwidth as a function of observation angle is also analyzed for the droplet-target plasma. The simulated plasma state parameter distributions and EUV spectral results closely match existing experimental data, demonstrating the ability of RHDLPP code to model laser-produced Sn plasma EUV light sources. These findings provide valuable support for the development of EUV lithography and EUV light sources.
SPECIAL TOPIC—Dynamics of atoms and molecules at extremes
2025, 74 (3): 033301.
doi: 10.7498/aps.74.20241400
Abstract +
Femtosecond laser-induced excitation of molecular rotational states can lead to phenomena such as alignment and orientation, which fundamentally stem from the coherence between the induced rotational states. In recent years, the quantitative study of coherence in the field of quantum information has received widespread attention. Different kinds of coherence measures have been proposed and investigated. In this work, the quantitative correlation is investigated in detail between the intrinsic coherence measurement and the degree of molecular alignment induced by femtosecond laser pulses at finite temperatures. By examining the molecular alignment induced by ultrafast non-resonant laser pulses, a quantitative relationship is established between the $l_1$ norm coherence measure $C_{l_1}(\rho)$ and the alignment amplitude ${\cal{D}}\langle \cos^2 \theta \rangle$. Here, $C_{l_1}(\rho)$ represents the sum of the absolute values of all off-diagonal elements of the density matrix ρ, ${\cal{D}}\langle \cos^2 \theta \rangle$ represents the difference between the maximum alignment and the minimum alignment. A quadratic relationship $ C_{l_1} = (a + b{\cal{E}}^2_0)\times $$ {\cal{D}}\langle \cos^2 \theta \rangle$ between the the $l_1$ norm coherence measure and ${\cal{D}}\langle \cos^2 \theta \rangle$ with respect to the electric field intensity ${\cal{E}}_0$ is obtained. This relationship is validated through numerical simulations of the CO molecule, and the ratio coefficients a and b for different temperatures are obtained. Furthermore, a mapping relationship between this ratio and the pulse intensity area is established. The findings of this study provide an alternative method for experimentally detecting the coherence measure within femtosecond laser-excited rotational systems, thereby extending the potential applicability of molecular rotational states to the study of the coherence measure in the field of quantum resources. This will facilitate the interdisciplinary integration of ultrafast strong-field physics and quantum information.
SPECIAL TOPIC—Dynamics of atoms and molecules at extremes
2025, 74 (3): 033401.
doi: 10.7498/aps.74.20241467
Abstract +
SPECIAL TOPIC—Dynamics of atoms and molecules at extremes
2025, 74 (3): 033402.
doi: 10.7498/aps.74.20241638
Abstract +
Bremsstrahlung, as an important radiation process in atomic physics, has significant applications in the fields of astrophysics, plasma physics, magnetic and inertial confinement fusion. In this work, the relativistic partial-wave expansion method is used to investigate the bremsstrahlung of neutral carbon atoms and different charged carbon ions scattered from intermediate- and high-energy relativistic electrons, with special attention paid to the electronic screening effect produced by the target electrons. The target wave function is obtained from the Dirac-Hartree-Fock self-consistent calculations, and the electron-atom scattering interaction potential is constructed in the central-field approximation. By solving the partial-wave Dirac equation, the continuum wave functions of the relativistic electron are obtained, from which the bremsstrahlung single and double differential cross sections can be calculated via the multipole free-free transitions between the incident and exit free electrons. The target electronic screening effects on the bremsstrahlung single and double differential cross sections are analyzed under a variety of conditions of incident electron energy and emitted photon energy. It is shown that the target electronic screening effect will significantly suppress the cross sections both at low incident energy and in the soft-photon region. Such a suppressing effect decreases with the incident electron energy and the emitted photon energy gradually increasing. Overall, the electronic screening effect has no significant influence on the shape function of bremsstrahlung.
INSTRUMENTATION AND MEASUREMENT
2025, 74 (3): 033701.
doi: 10.7498/aps.74.20241348
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High-finesse optical cavity assisted quantum nondemolition (QND) measurement is an important method of generating high-gain spin or momentum squeezed states, which can enhance the sensitivity of atom interferometers beyond the standard quantum limit. Conventional two-mirror Fabry-Perot cavities have the drawback of a standing wave pattern, leading to inhomogeneous atom-light coupling and subsequent degradation of metrological gain. In this study, we present a novel method of achieving homogeneous quantum nondemolition measurement by using an optical ring cavity to generate momentum squeezed states in atom interferometers. We design and develop a high-finesse ($ {\cal{F}} = 2.4(1) \times 10^{4} $), high-vacuum compatible ($ 1\times 10^{-10} \;{\rm mbar}$) optical ring cavity. It utilizes the properties of traveling wave fields to address the issue of inhomogeneous atom-light interaction. A strontium cold atomic ensemble is prepared and coupled into the cavity mode; the nondemolition measurement of atom number is achieved by extracting the dispersive cavity phase shift caused by the passage of atoms through differential Pound-Drever-Hall measurement. Experimental results indicate that under a probe laser power value of 20 μW, the dispersive phase shift of the ring cavity is measured to be 40 mrad. The effective number of atoms coupled into the cavity mode is around $ 1 \times 10^{5} $. The consistency between the ring cavity dispersive phase shift and QND measurement theory is verified by adjusting parameters such as matching the atomic position with the cavity mode and tuning the frequency of the probe laser. The optical ring cavity developed in this work provides an important method for generating spin or momentum squeezed states in atom interferometers. Therefore it holds promise for enhancing their sensitivity, and it is expected to be widely applied to cavity-enhanced quantum precision measurements.
ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
2025, 74 (3): 034101.
doi: 10.7498/aps.74.20241516
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In this work, a tunable perfect absorber in the terahertz range is designed based on Dirac semimetal nanowires, featuring high sensitivity, quality factor, and dual functionality. The absorber achieves perfect absorptions across seven bands in a range of 0–14.5 THz: f1 = 5.032 THz (84.43%), f2 = 5.859 THz (96.23%), f3 = 7.674 THz (91.36%), f4 = 9.654 THz (99.02%), f5 = 11.656 THz (93.84%), f6 = 12.514 THz (98.47%), and f7 = 14.01 THz (97.32%). To ensure structural stability during design, the periodicity of the wire array structure is carefully considered. Verification of the absorber’s performance is conducted through the calculation of impedance matching. The analyses of the surface electric field and magnetic field at resonance frequency elucidate the underlying physical mechanisms governing the absorber’s characteristics. The values of quality factor (Q) for the seven resonance points are computed, with a maximum Q of 219.41. Further investigations by changing the external refractive index show that the maximum sensitivity value and the figure of merit (FOM) value are 5421.43 GHz/RIU and 35.204 RIU–1, respectively. Then, by discussing the influence of key parameters on the device, we conclude that the device can achieve the choice of dual fixed performance. Dynamic modulation capabilities are demonstrated by changing the Dirac semimetal’s Fermi energy. Additionally, by changing the incident angle of the external electromagnetic wave, it is found that the device has good stability in the medium frequency band and low frequency band, but it is greatly affected by the external incident angle in the high frequency band, thus necessitating careful consideration in practical applications. In conclusion, the proposed absorber holds significant promise for imaging, sensing, and detection applications, providing the valuable insights for designing optoelectronic devices.
ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
2025, 74 (3): 034201.
doi: 10.7498/aps.74.20241349
Abstract +
Terahertz (THz) waves have been widely investigated recently due to their ability to reflect the fingerprint characteristics of samples. As a promising method, THz technology has aroused great interest in various applications, especially biological imaging, environmental monitoring, non-destructive evaluation, spectroscopy and molecular analysis. In order to reveal the intramolecular vibration/rotation information of various compounds, the linewidths of their absorption lines are usually in a range of GHz or even MHz, and THz waves with wide tunability, narrow linewidth, high frequency accuracy, and high power stability are required. Currently, the linewidth with GHz level and low SNR at higher frequency still limit its further applications in reveal intramolecular information. In this work, the thermal distribution characteristics of DAST crystals based on diamond substrates under continuous laser pumping conditions are theoretically studied by COMSOL Multiphysics, and the effectiveness of diamond substrates in dissipating heat from DAST crystals is experimentally verified. Then, a narrow-linewidth and tunable organic-crystal continuous-wave terahertz source is demonstrated. Two narrow-linewidth continuous-wave (CW) fiber lasers are used as the pump sources for generating difference frequency. The terahertz wave is continuously tunable in a range of 1.1–3 THz. The maximum output power of 3.39 nW is obtained at 2.493 THz. The power fluctuation in 30 min is measured to be 2.19%. In addition, the generated THz wave has a high polarization extinction ratio of 9.44 dB. Using this CW-THz source for high-precision spectral detection of air with different humidity, the results correspond well with the gas absorption spectral lines in the Hitran database, proving that the CW-THz source has narrow linewidth, high frequency accuracy and stability. Therefore, it can promote the practical application of tunable CW-THz source, thus having good potential in THz high-precision spectroscopic detection and multispectral imaging.
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