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<jats:p>As the signal reflected by the corner-cube reflector arrays is very weak and easily submerged during the full moon, we analyze the influence of the thermal effect of corner-cube reflector arrays on the intensity of lunar laser ranging echo. Laser ranging measurements during the penumbra lunar eclipse verify suspected thermal deformation in the Lunakhod 2 reflectors. Signal levels vary over two orders of magnitude as the penumbra eclipse progresses. This can be explained by the change in the dihedral angle of the corner-cube reflectors caused by the temperature. The results show that when the dihedral angle errors reach 1″, the energy is reduced by 100 times compared with the ideal corner-cube reflector. In the experiment, our findings suggest that when the corner-cube reflector arrays enter the penumbra of the earth, the effective echo signal level which reaches 0.18 photons/s far exceeds the historical level of the full moon. However, 11 minutes after the penumbra lunar eclipse, the effective echo rate of Lunakhod 2 will drop two orders of magnitude. The mechanism can explain the acute signal deficit observed at full moon.</jats:p>

<jats:p>With the rapid development of terahertz technology, terahertz detectors are expected to play a key role in diverse areas such as homeland security and imaging, materials diagnostics, biology, medical sciences, and communication. Whereas self-powered, rapid response, and room temperature terahertz photodetectors are confronted with huge challenges. Here, we report a novel rapid response and self-powered terahertz photothermoelectronic (PTE) photodetector based on a low-dimensional material: palladium selenide (PdSe<jats:sub>2</jats:sub>). An order of magnitude performance enhancement was observed in photodetection based on PdSe<jats:sub>2</jats:sub>/graphene heterojunction that resulted from the integration of graphene and enhanced the Seebeck effect. Under 0.1-THz and 0.3-THz irradiations, the device displays a stable and repeatable photoresponse at room temperature without bias. Furthermore, rapid rise (5.0 μs) and decay (5.4 μs) times are recorded under 0.1-THz irradiation. Our results demonstrate the promising prospect of the detector based on PdSe<jats:sub>2</jats:sub> in terms of air-stable, suitable sensitivity and speed, which may have great application in terahertz detection.</jats:p>

<jats:p>In recent years, gas electron multiplier (GEM) neutron detectors have been developing towards high spatial resolution and high dynamic counting range. We propose a novel concept of an Al stopping layer to enable the detector to achieve sub-millimeter (sub-mm) spatial resolution. The neutron conversion layer is coated with the Al stopping layer to limit the emission angle of ions into the drift region. The short track projection of ions is obtained on the signal readout board, and the detector would get good spatial resolution. The spatial resolutions of the GEM neutron detector with the Al stopping layer are simulated and optimized based on Geant4GarfieldInterface. The spatial resolution of the detector is 0.76 mm and the thermal neutron detection efficiency is about 0.01% when the Al stopping layer is 3.0 μm thick, the drift region is 2 mm thick, the strip pitch is 600 μm, and the digital readout is employed. Thus, the GEM neutron detector with a simple detector structure and a fast readout mode is developed to obtain a high spatial resolution and high dynamic counting range. It could be used for the direct measurement of a high-flux neutron beam, such as Bragg transmission imaging, very small-angle scattering neutron detection and neutron beam diagnostic.</jats:p>

<jats:p>Potential energy curves of the X<jats:sup>1</jats:sup>Σ<jats:sup>+</jats:sup> and A<jats:sup>1</jats:sup>Π states of the AlF molecule are studied through the combination of the multi-reference configuration interaction (MRCI) approach and Davidson corrections (MRCI+Q). The AWCV5Z basis set is employed in the calculations. The transition dipole moments (TDMs) of the A<jats:sup>1</jats:sup>Π ↔ X<jats:sup>1</jats:sup>Σ<jats:sup>+</jats:sup> transition are explored based on the AWCV5Z basis set and (4, 2, 2, 0) active space. The Schrödinger equation is solved via the LEVEL 8.2 program, and the vibrational levels and rotational constants of the X<jats:sup>1</jats:sup>Σ<jats:sup>+</jats:sup> and A<jats:sup>1</jats:sup>Π states are calculated. It is shown that the AlF molecule has high diagonal Franck–Condon factors (<jats:italic>f</jats:italic> <jats:sub>00</jats:sub> = 0.9949 and <jats:italic>f</jats:italic> <jats:sub>11</jats:sub> = 0.9854) and large Einstein coefficients for the transition of A<jats:sup>1</jats:sup>Π (<jats:italic>ν</jats:italic>′ = 0) ↔ X<jats:sup>1</jats:sup>Σ<jats:sup>+</jats:sup> (<jats:italic>ν</jats:italic>″ = 0). In addition, the radiative lifetimes of the vibrational levels are close to 10<jats:sup>−9</jats:sup> s for the A<jats:sup>1</jats:sup>Π state. The line intensities of the A<jats:sup>1</jats:sup>Σ (<jats:italic>ν</jats:italic>′ = 4 – 15) ↔ X<jats:sup>1</jats:sup>Σ<jats:sup>+</jats:sup> (<jats:italic>ν</jats:italic>″ = 0) transitions are also calculated. The calculated TDMs and transition probabilities in this work are credible and provide some guidance for the study of similar transitions, particularly for exploring interstellar space.</jats:p>

<jats:p>Atomic data of highly charged ions (HCIs) offer an attractive means for plasma diagnostic and stars identification, and the investigations on atomic data are highly desirable. Herein, based on the fully relativistic multi-configuration Dirac–Hartree–Fock (MCDHF) method, we have performed calculations of the fine-structure energy levels, wavelengths, transition rates, oscillator strengths, and line strengths for the lowest 21 states of 3p<jats:sup>6</jats:sup>3d<jats:sup>8</jats:sup>–3p<jats:sup>5</jats:sup>3d<jats:sup>9</jats:sup> electric dipole (E1) transitions configurations in Fe-like ions (<jats:italic>Z</jats:italic> = 57, 60, 62, 64, 65). The correlation effects of valence–valence (VV) and core–valence (CV) electrons were systematically considered. In addition, we have taken into account transverse-photon (Breit) interaction and quantum electrodynamics (QED) corrections to treat accurately the atomic state wave functions in the final relativistic configuration interaction (RCI) calculations. Our calculated energy levels and transition wavelengths are in excellent agreement with the available experimental and theoretical results. Most importantly, we predicted some new transition parameters that have not yet been reported. These data would further provide critical insights into better analyzing the physical processes of various astrophysical plasmas.</jats:p>

<jats:p>To improve two-photon absorption (TPA) response of a newly synthesized probe, a series of ratiometric two-photon fluorescent Zn<jats:sup>2+</jats:sup> sensors based on quinoline and DPA moieties have been designed. The one-photon absorption, TPA, and emission properties of the experimental and designed probes before and after coordination with Zn<jats:sup>2+</jats:sup> are investigated employing the density functional theory in combination with response functions. The design consists of two levels. In the first level of design, five probes are constructed through using several electron acceptors or donors to increase accepting or donating ability of the fluorophores. It shows that all the designed probes have stronger TPA intensities at longer wavelengths with respect to the experimental probe because of the increased intra-molecular charge transfer. Moreover, it is found that the probe 4 built by adding an acyl unit has the largest TPA cross section among the designed structures due to the form of longer conjugated length and more linear backbone. One dimethylamino terminal attached along the skeleton can improve TPA intensity more efficiently than two side amino groups. Therefore, in the second level of design, a new probe 7 is formed by both an acyl unit and a dimethylamino terminal. It exhibits that the TPA cross sections of probe 7 and its zinc complex increase dramatically. Furthermore, the fluorescence quantum yields of the designed probes 4 and 7 are calculated in a new way, which makes use of the relation between the computed difference of dipole moment and the measured fluorescence quantum yield. The result shows that our design also improves the fluorescence quantum yield considerably. All in all, the designed probes 4 and 7 not only possess enhanced TPA intensities but also have large differences of emission wavelength upon Zn<jats:sup>2+</jats:sup> coordination and strong fluorescence intensity, which demonstrates that they are potential ratiometric two-photon fluorescent probes.</jats:p>

<jats:p>We consider an extremely intense laser, enclosed by an atom interferometer. The gravitational potential generated from the high-intensity laser is solved from the Einstein field equation under the Newtonian limit. We compute the strength of the gravitational force and study the feasibility of measuring the force by the atom interferometer. The intense laser field from the laser pulse can induce a phase change in the interferometer with Bose–Einstein condensates. We push up the sensitivity limit of the interferometer with Bose–Einstein condensates by spin-squeezing effect and determine the sensitivity gap for measuring the gravitational effect from intense laser by atom interferometer.</jats:p>

<jats:p>Manipulating directional electromagnetic scattering plays a crucial role in the realization of exotic optical phenomenon. Here, we show that the spoof plasmonic structure is able to achieve the switching of directional scattering direction on a subwavelength scale by inserting a perfect electric conductor (PEC) cylinder into the hollow of the spoof plasmonic structure. Based on the modal analysis, it is found that the electromagnetic response of the core–shell structure not only is well excited, but also exhibits the directional scattering by interference between the electric and magnetic dipolar resonances. We also discuss the influence of PEC cylinder radius on the performance of the directional scattering. Finally, the active tunable directional scattering is realized by switching between the two states. This work provides a feasible pathway to the subwavelength manipulation of electromagnetic wave. Moreover, it offers a simple method to switch the directional scattering direction. The proposed design approach can be easily applied to digital electromagnetic wave communication and associated applications.</jats:p>

<jats:p>A miniaturized multi-frequency circularly polarized array is designed in this paper. The antenna array is composed of three independent sub-arrays employing modified quarter-mode substrate ntegrated aveguide (QMSIW) to achieve three circularly polarized frequency bands. By introducing strip-slot, the impedance bandwidth of the antenna array is broadened while the dimension is decreased by 75% to realize miniaturization. Meanwhile, metasurface causes the impedance bandwidth of the sub-array to be further enhanced. Moreover, the metal vias are employed in the antenna array design to further achieve miniaturization. The antenna array is manufactured and measured to verify the design. Both the measured and simulated results display that the array achieves the impedance bandwidths of 10%, 11.7%, and 14.8% and axial ratio bandwidths of 8.8%, 8.0%, and 8.5% at 2.5, 3.5, and 4.8 GHz, respectively. The gain is stable in the operating band within an uncertainty of 0.7 dBi. The whole dimension is 0.92<jats:italic>λ</jats:italic> × 0.63<jats:italic>λ</jats:italic> × 0.04<jats:italic>λ</jats:italic>, where <jats:italic>λ</jats:italic> <jats:sub>0</jats:sub> is the wavelength at the lowest resonant frequency. Furthermore, the simple structure and miniaturization provides great convenience in sub-6 applications.</jats:p>

<jats:p>In electron beam technology, one of the critical focuses of research and development efforts is on improving the measurement of electron beam parameters. The parameters are closely related to the generation, emission, operation environment, and role of the electron beam and the corresponding medium. In this study, a field calculation method is proposed, and the electric field intensity distribution on the electron beam’s cross-section is analyzed. The characteristics of beam diffusion caused by the space charge effect are investigated in simulation, and the obtained data are compared with the experiment. The simulation demonstrated that the cross-sectional electric field distribution is primarily affected by the electron beam current, current density distribution, and electron beam propagation speed.</jats:p>