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Electromagnetically Induced Transparency In Rydberg Atomic Medium
摘要： Due to possessing big principal quantum number, Rydberg atom has some unique properties, for example： its radiative lifetime is long, dipole moment is large, and interaction between atoms is strong and so on. These properties make one pay attention to Rydberg atoms. In this paper we investigate the effects of Rydberg dipole-dipole interactions on electromagnetically induced transparency (EIT) schemes and group velocity in three-level systems of ladder type, which provides theoretical foundation for exploring the linear and nonlinear characteristics of light in a Rydberg electromagnetically-induced-transparency medium.
关键词： group velocity,Rydberg atom,electromagnetically induced transparency,dipole-dipole interactions
更新于2025-09-09 09:28:46
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Characteristics of krypton ion emission from a gas field ionization source with a single atom tip
摘要： A scanning ion beam instrument equipped with a gas ?eld ionization source (GFIS) has been commercialized, but only helium and neon are currently available as GFISs. The characteristics of krypton ion emission from a single atom tip (SAT) have not been reported yet. In this study, the characteristics of krypton ion emission were investigated by ?eld ion microscopy. At 65 K, the krypton ion emission current reached approximately 40 pA, which is 1 order of magnitude higher than that at 130 K. As the krypton gas pressure was increased, the krypton ion current increased. At a pressure of 0.3 Pa, the emission current was anticipated to reach 200 pA, which may be high enough for nanofabrication. The variation of the krypton ion current was as low as 5% in one hour. We concluded that a krypton ion beam instrument equipped with a GFIS will be a powerful tool for nanofabrication.
关键词： gas field ionization source,field ion microscopy,nanofabrication,single atom tip,krypton ion emission
更新于2025-09-09 09:28:46
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Quantum radiation from a shaken two-level atom in vacuum
摘要： We present a nonrelativistic theory of quantum radiation generated by shaking a two-level atom in vacuum. Such radiation has the same origin of photon emission in dynamical Casimir effect. By performing a time-dependent “dressing” transformation to the Hamiltonian, we derive an interaction term that governs the radiation. In particular, we show that photon pairs can be generated, not only by shaking the position of the atom, but also by changing the internal states of the atom. As applications of our theory, we calculate the emission rate from an oscillating atom and the multiphoton state generated in a single-photon scattering process.
关键词： time-dependent dressing transformation,two-level atom,dynamical Casimir effect,quantum radiation,photon emission
更新于2025-09-09 09:28:46
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Perturbation Theory in the Analysis of Quantum Vortices Formed by Impact of Ultrashort Electromagnetic Pulse on Atom
摘要： Nonstationary perturbation theory is used to study generation of quantum vortices resulting from ionization of hydrogen-like atom by an ultrashort pulse of classical electromagnetic field. It is shown that the vortices are determined by quantum interference effects.
关键词： quantum vortices,hydrogen-like atom,quantum interference effects,classical electromagnetic field,nonstationary perturbation theory,ultrashort pulse
更新于2025-09-09 09:28:46
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Photosensitization and Photocatalysis - Perspectives in Organic Synthesis
摘要： Photochemical sensitization and photocatalysis have very similar definitions and are closely related. Each of the two terms are preferentially used in different scientific communities. Three types of processes are discussed: (1) sensitization involving energy transfer, (2) photocatalysis in which hydrogen abstraction plays a key role and (3) photoredox catalysis in which electron transfer is involved. The processes are discussed in connection with [2+2] photocycloadditions and C-H activation, which are of particular interest for organic synthesis.
关键词： [2+2] Photocycloaddition,Photosensitization,Energy transfer,Hydrogen atom transfer,Electron transfer,C-H activation,Photocatalysis
更新于2025-09-09 09:28:46
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Surface plasmon induced atom localization in a tripod-type four level atomic system
摘要： We demonstrate the phenomenon of atom localization using surface plasmon polariton absorption/dispersion spectrums. A single and double localized peaks are measured on the absorption/dispersion spectrums of surface plasmon polariton at di?erent parameters and directions of propagation of the control ?elds. We show localized peaks with ～ 80% probability on dispersion spectrum and 50 % probability on the absorption spectrum. The localized peaks observed are shown to depend on strength of the control ?eld and the electrical conductivity.
关键词： surface plasmon polariton,atom localization,electrical conductivity,control ?elds,absorption/dispersion spectrums
更新于2025-09-09 09:28:46
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Object Recognition Based on Wave Atom Transform
摘要： This study presents an efficient method for recognizing object in an image based on Wave Atom Transform (WAT). Object recognition is achieved by extracting the energies from all coefficients of WAT. The original image is decomposed by using the WAT. All coefficients are considered as features for the classification process. The extracted features are given as an input to the K-Nearest Neighbor (K-NN) classifier to recognize the object. The evaluation of the system is carried on using Columbia Object Image Library Dataset (COIL-100) database. The classification performance of the proposed system is evaluated by using classification rate in percentage, which is achieved by varying the angle between the views.
关键词： feature extraction,Classification rate,object recognition,wave atom transform,KNN classifier
更新于2025-09-09 09:28:46
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Guiding of light with pinholes
摘要： A new type of light waveguide using linearly aligned pinholes is presented. Results of basic experiments are compared with theoretical estimates calculated using continuous model. This model predicts that the loss per unit length of the light inside this waveguide is proportional to the square root of the spacing between the pinholes. Since this waveguide utilizes no transparent material, it can be used to guide electromagnetic waves of wide wavelength ranges as well as other waves such as matter waves.
关键词： Waveguide,atom optics,diffraction optics
更新于2025-09-09 09:28:46
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Direct Imaging of Photo-Switching Molecular Conformations Using Individual Metal Atom Markers
摘要： Photo-switching behavior of individual organic molecules was imaged by annular dark-field scanning transmission electron microscopy (ADF-STEM) using a highly electron beam transparent graphene support. Photo-switching azobenzene derivatives with ligands at each ends containing single transition metal atoms (Pt) were designed (Pt-complex), and the distance between the strong ADF-STEM contrast from the two Pt atoms in each Pt-complex is used to track molecular length changes. UV irradiation was used to induce photo-switching of the Pt complex on graphene, and we show that the measured Pt-Pt distances within isolated molecules decreases from ~2.1 nm to ~1.4 nm, indicative of a trans-to-cis isomerization. Light illumination of the Pt-complex on the graphene support also caused their diffusion out from initial clusters to the surrounding area of graphene, indicating that the light-activated mobilization overcomes the inter-molecular van der Waals interactions. This approach shows how individual isolated heavy metal atoms can be included as markers into complex molecules to track their structural changes using ADF-STEM on graphene supports, providing an effective method to study a diverse range of complex organic materials at the single molecule level.
关键词： annular dark-field scanning transmission electron microscopy,photo-switch,direct imaging,graphene support,heavy atom marker,azobenzene
更新于2025-09-09 09:28:46
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Can BODIPY Dimers Act as Photosensitizers in Photodynamic Therapy? A Theoretical Prediction
摘要： The photophysical properties of some monomeric and dimeric BODIPY systems were investigated at the density functional theory level and herein reported. In particular, the absorption spectra were fully characterized, low energy singlet and triplet excited states were discussed also focusing on the energy difference gaps between them and computing the spin-orbit couplings values for the possible intersystem crossing channels. The heavy atom effect of iodine substituents on the photophysical properties of a monomer and on a dimer under investigation was also estimated. Results obtained on the considered compounds allow us to predict which is the most promising candidate to be suggested as a photosensitizer in photodynamic therapy.
关键词： BODIPY,PDT,heavy atom effect,TDDFT,spin-orbit coupling
更新于2025-09-04 15:30:14