Microwave Electrometry with Rydberg Eletromagnetically Induced Transparency in Vapor Cells

An atom-based approach is presented to detect absolute microwave (MW) electric fields (E-fields). The approach uses Rydberg atoms in vapor cells at room temperature. The MW E-field measurements utilize a bright resonance prepared within an electromagnetically induced transparency (EIT) window. The large transition dipole moments between energetically adjacent Rydberg states enable this method to make traceable E-field measurements with a sensitivity that is several orders of magnitude higher than the current standard for MW E-field measurements. The method can be used to image MW E-field in the near field regime with a subwavelength resolution of $\mathrm{\lambda_{MW}/650}$, where $\mathrm{\lambda_{MW}}$ is the wavelength of the MW E-field. A high accuracy of $\mathrm{1\%}$ has been reached by minimizing the effects of the vapor cell geometry on the measured MW E-field. The dissertation also presents an alternative technique to perform the MW E-field measurement using dispersive properties of the EIT spectrum with a prism vapor cell. Recently, we applied a homodyne detection technique with a Mach Zehnder interferometer to achieve a new sensitivity limit for the MW E-field measurement, $\mathrm{\sim3~\mu Vcm^{-1}Hz^{-1/2}}$. The new sensitivity is one order of magnitude better than our prior best sensitivity presented in Ref. [Nat. Phys. 8, 819 (2012)]. The Rydberg atom-based method is promising to be a new standard for MW E-field measurements and to develop into portable devices in the field of MW technologies

Sensitivity Comparison of Two-photon vs Three-photon Rydberg Electrometry

We investigate the sensitivity of three-photon EIT in Rydberg atoms to radio frequency detection and compare it against conventional two-photon systems. Specifically, we model the 4-level and 5-level atomic system and compare how the transmission of the probe changes with different powers of the lasers used and strengths of the RF field. In this model, we also define a sensitivity metric to best relate to the operation of the current best experimental implementation based on shot noise limited detection. We find that the three-photon system boasts much narrower line widths compared to the conventional two-photon EIT. However, these narrow line features do not align with the regions of the best sensitivity. In addition to this, we calculate the expected sensitivity for the two-photon Rydberg sensor and find that the best achievable sensitivity is over an order of magnitude better than the current measured values of 5 uV/m/Hz. However, by accounting for the additional noise sources in the experiment and the quantum efficiency of the photo-detectors, the values are in good agreement.Comment: 9 pages, 6 figure

assessmentofcontemporarytheoreticalmethodsforbonddissociationenthalpies

计算键解离焓的方法除了对很小的体系采用高精度量子化学方法外，最常使用的便是密度泛函方法（DFT）．但是碍于其计算精度有限，因此希望能寻找到适合处理较大体系且精度更高的理论方法．本文考察的方法有DFT、双杂化密度泛函方法、以及高精度方法，所研究的对象包括了单环及多环芳香化合物、支链烷烃、以及小的无机化合物分子等．结果表明，所有方法中，mPW2PLYP方法和G4MP2方法的综合表现最好．根据计算结果，最后建议在计算小尺寸的体系（原子数〈20）时，选择G4MP2方法；计算大尺寸f20≤原子数〈50）的芳香化合物时，双杂化密度泛函方法最为适宜，计算在此尺寸范围内的长链或支链烷烃时，适宜选择有经验色散校正的双杂化密度泛函方法；处理更大尺寸（原子数≥50）的体系时，建议使用DFT方法，其中M06—2X方法和B3P86方法均有不错表现．此外，不同方法的最优结构的差别以及基组的影响均在考察内容中

In situ assembly of zeolite nanocrystals into mesoporous aggregate with single-crystal-like morphology without secondary template

The formation of zeolite crystal its subsequent assembly into a mesoporous aggregate by enhancing the zeolite nucleation rate was demonstrated. ZSM-12 was selected that has micropores that are slightly larger and during the synthesis of ZSM-12 crystals and a mesoporous aggregate of ZSM-12 nanocrystals with a morphology similar to common ZSM-12 was obtained. The hydrothermal stability of ZSM-12 was tested by refluxing in boiling water for 120 hours with a sample-to-water ratio of 1:10 and by increasing the crystallization time to 8 days. The meso- and microstructure of mesoporous ZSM-12 was found to be stable during the treatments that was confirmed by powder X-ray diffraction images and scanning electron microscopy. The results indicate that the mesoporous ZSM-12 is highly hydrothermally stable that is important for the industrial catalytic applications

assessmentofcontemporarytheoreticalmethodsforbonddissociationenthalpies

计算键解离焓的方法除了对很小的体系采用高精度量子化学方法外，最常使用的便是密度泛函方法（DFT）．但是碍于其计算精度有限，因此希望能寻找到适合处理较大体系且精度更高的理论方法．本文考察的方法有DFT、双杂化密度泛函方法、以及高精度方法，所研究的对象包括了单环及多环芳香化合物、支链烷烃、以及小的无机化合物分子等．结果表明，所有方法中，mPW2PLYP方法和G4MP2方法的综合表现最好．根据计算结果，最后建议在计算小尺寸的体系（原子数〈20）时，选择G4MP2方法；计算大尺寸f20≤原子数〈50）的芳香化合物时，双杂化密度泛函方法最为适宜，计算在此尺寸范围内的长链或支链烷烃时，适宜选择有经验色散校正的双杂化密度泛函方法；处理更大尺寸（原子数≥50）的体系时，建议使用DFT方法，其中M06—2X方法和B3P86方法均有不错表现．此外，不同方法的最优结构的差别以及基组的影响均在考察内容中

Porous Au–Ag Nanospheres with High-Density and Highly Accessible Hotspots for SERS Analysis

Colloidal plasmonic metal nanoparticles have enabled surface-enhanced Raman scattering (SERS) for a variety of analytical applications. While great efforts have been made to create hotspots for amplifying Raman signals, it remains a great challenge to ensure their high density and accessibility for improved sensitivity of the analysis. Here we report a dealloying process for the fabrication of porous Au–Ag alloy nanoparticles containing abundant inherent hotspots, which were encased in ultrathin hollow silica shells so that the need of conventional organic capping ligands for stabilization is eliminated, producing colloidal plasmonic nanoparticles with clean surface and thus high accessibility of the hotspots. As a result, these novel nanostructures show excellent SERS activity with an enhancement factor of ∼1.3 × 10⁷ on a single particle basis (off-resonant condition), promising high applicability in many SERS-based analytical and biomedical applications