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This article proposes a novel cetyltrimethylammonium bromide-and fluorine-assisted hydrothermal deposition method for modulating the morphology of supported metal nanoparticles in NiWF/Al 2 O 3 hydrodesulfurization (HDS) catalysts. The proposed approach significantly promotes the dispersion of supported W species by bridging and anchoring the precursor of W species onto the surface of fluorinated Al 2 O 3 as well as restraining the subsequent aggregation of W species in calcination. The dual effects of the improved dispersion and F-enhanced stacking endow the corresponding catalyst with superior morphology featured by sufficient and accessible Ni-W-S active phases and thereby with a remarkably promoted HDS performance as compared to its counterpart prepared by the conventional impregnation method. We successfully demonstrate the roles of the cetyltrimethylammonium bromide-and fluorine-assisted hydrothermal deposition method in tuning the morphology of supported metal nanoparticles in HDS catalysts, shedding light on the rational design and fabrication of supported metal sulfide catalysts.

We study Rydberg atoms modulated by strong radio-frequency (RF) fields with a frequency of 70 MHz. The Rydberg atoms are prepared in a room temperature cesium cell, and their level structure is probed using electromagnetically induced transparency (EIT). As the RF field increases from the weak-into the strong-field regime, the range of observed RF-induced phenomena progresses from AC level shifts through increasingly pronounced and numerous RF-modulation sidebands to complex state-mixing and level-crossings with high-l hydrogen-like states. Weak anharmonic admixtures in the RF field generate clearly visible modifications in the Rydberg-EIT spectra. A Floquet analysis is employed to model the Rydberg spectra, and good agreement with the experimental observations is found. Our results show that all-optical spectroscopy of Rydberg atoms in vapor cells can serve as an antenna-free, atom-based and calibration-free technique to measure and map RF electric fields and to analyze their higher-harmonic contents.

In order to obtain a metasurface structure capable of filtering light of a specific wavelength range in the visible band, the traditional methods usually traverse the space consisting of possible designs, searching for a potentially satisfactory structure by performing iterative calculations to solve Maxwell's equations. In this article, we propose a systematic method based on neural networks that can complete an inverse design process to solve the problem. Compared with the traditional methods, our method is much faster while competent to encompass a high degree of freedom to generate device structures, which can ensure that the spectra of generated structures resemble the desired ones.

Electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) are two similar yet distinct phenomena that modify the transmission of a weak probe field through an absorption medium in the presence of a coupling field, featured in a variety of three-level atomic systems. In many applications it is important to distinguish EIT from ATS splitting. We present EIT and ATS spectra in a three-level cascade system, involving cold cesium atoms in the S 35 1 2 Rydberg state. The EIT linewidth, γ EIT , defined as the full width at half maximum of the transparency window, and the ATS splitting, γ ATS , defined as the peak-to-peak distance between AT absorption peaks, are used to delineate the EIT and ATS regimes and to characterize the transition between the regimes. In the coldatom medium, in the weak-coupler (EIT) regime γ EIT ≈A + B( cwhere Ω c and Ω p are the coupler and probe Rabi frequencies, Γ eg is the spontaneous decay rate of the intermediate 6P 3/2 level, and parameters A and B that depend on the laser linewidth. We explore the transition into the strong-coupler (ATS) regime, which is characterized by the relation γ ATS ≈Ω c . The experiments are in agreement with numerical solutions of the Master equation. Our analysis accounts for non-ideal conditions that exist in typical realizations of Rydberg-EIT, including laser-frequency jitter, Doppler mismatch of the utilized two-color Rydberg EIT system, and strong probe fields. The obtained criteria to distinguish cold-atom EIT from ATS are readily accessible and applicable in practical implementations.

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