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Multipole Radiations from Large Gold Nanospheres Excited by Evanescent Wave
摘要： We proposed the use of the evanescent wave generated in a total internal reflection configuration to excite large gold nanospheres and investigated the radiations of the high-order plasmon modes supported in gold nanospheres. It was revealed that the evanescent wave excitation is equivalent to the excitation by using both the incident and reflected light, offering us the opportunity to control the orientation of the electric field used to excite nanoparticles. In addition, it was found that the scattering light intensity is greatly enhanced and the background noise is considerably suppressed, making it possible to detect the radiations from high-order plasmon modes. Moreover, the influence of the mirror images on the scattering induced by a metal substrate is eliminated as compared with the surface plasmon polariton excitation. By exciting a gold nanosphere with s-polarized light and detecting the scattering light with a p-polarized analyzer, we were able to reveal the radiation from the electric quadrupole mode of the gold nanosphere in both the spatial and the frequency domains. Our findings are important for characterizing the radiations from the high-order modes of large nanoparticles and useful for designing nanoscale photonic devices.
关键词： scattering,plasmon mode,electric dipole,radiation pattern,gold nanosphere,evanescent wave,electric octupole,electric quadrupole
更新于2025-11-21 11:24:58
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Generalized perspective on chiral measurements without magnetic interactions
摘要： We present a unified description of several methods of chiral discrimination based exclusively on electric-dipole interactions. It includes photoelectron circular dichroism (PECD), enantiosensitive microwave spectroscopy (EMWS), photoexcitation circular dichroism (PXCD), and photoelectron-photoexcitation circular dichroism (PXECD). We show that, in spite of the fact that the physics underlying the appearance of a chiral response is very different in all these methods, the enantiosensitive and dichroic observable in all cases has a unique form. It is a polar vector given by the product of (i) a molecular pseudoscalar and (ii) a field pseudovector specified by the configuration of the electric fields interacting with the isotropic ensemble of chiral molecules. The molecular pseudoscalar is a rotationally invariant property, which is composed from different molecule-specific vectors and in the simplest case is a triple product of such vectors. The key property that enables the chiral response is the noncoplanarity of the vectors forming such triple product. The key property that enables chiral detection without relying on the chirality of the electromagnetic fields is the vectorial nature of the enantiosensitive observable. Our compact and general expression for this observable shows what ultimately determines the efficiency of the chiral signal and if, or when, it can reach 100%. We also discuss the differences between the two phenomena, which rely on the bound states, PXCD and EMWS, and the two phenomena using the continuum states, PECD and PXECD. Finally, we extend these methods to arbitrary polarizations of the electric fields used to induce and probe the chiral response.
关键词： photoelectron-photoexcitation circular dichroism,electric-dipole interactions,field pseudovector,enantiosensitive microwave spectroscopy,photoexcitation circular dichroism,molecular pseudoscalar,chiral discrimination,photoelectron circular dichroism
更新于2025-09-23 15:23:52
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Study of the Electronic and Electrical Properties of the C60F18 Polar Molecule on Au(111) Surface
摘要： For adequate description of the adsorption and self-assembly of C60F18 polar molecules on the surface Au(111), quantum-chemical studies of the electronic and electrical properties of a single molecule are performed. Using various procedures of density functional theory, the electric dipole moment of the molecule, distributions of the electrostatic potential, electric-field magnitude and electron density are calculated with controlled accuracy for the first time. An improved value of the electric dipole moment of the C60F18 molecule is obtained in a range from 10 to 11 D. The known approximation of a point dipole for electric-field strength is shown to be fulfilled within an accuracy of 30% even at distances twice greater than the size of the molecule. The structural fragments of the calculated lowest unoccupied and highest occupied molecular orbitals are assigned to their images, which were previously obtained using scanning tunneling microscopy and spectroscopy.
关键词： density functional theory,lowest unoccupied and highest occupied molecular orbitals,electric dipole moment,scanning tunneling spectroscopy,fullerene fluoride
更新于2025-09-23 15:23:52
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Time Domain Modelling of Pulse Wave Scattering on Small Metal Spheres
摘要： We consider a short pulse plane wave incident on a small metal sphere. The scattered field from the sphere can be presented as a multipole expansion over spherical harmonics. For small spheres (compared to the signal duration) the scattered field will be mainly presented by the dipole component. So we find in a closed form and analyze the convolution operator that relates the induced dipole moment (both electric and magnetic dipoles are considered) to the incident electric field waveform. The numerical approach to calculate scattering from several such spheres is described.
关键词： transient electric dipole,discrete dipole approximation,induced dipole moment,closed-form solution,transient diffraction
更新于2025-09-23 15:21:21
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A wideband aperture coupled magnetoa??electric dipole with high gain stability
摘要： In this article, a wideband aperture coupled magneto-electric (ME) dipole is proposed. The proposed dipole antenna is based on the traditional ME dipole which consists a pair of horizontal patches and a pair of vertical shorted patches. To achieve a wide impedance bandwidth, a stepped microstrip to slot transition is introduced in the antenna. Then, the vertical part of the dipole is tilted and two metal triangular prisms are employed to enhance the stability of the gain. A prototype antenna is fabricated and tested. Good agreements are found between the simulated and measured results. The measured impedance bandwidth for VSWR ≤2 is more than 125% (2.24-10.0 GHz). The 1 dB gain bandwidth is about 108% (2.4-8.0 GHz). Moreover, a stable unidirectional radiation patterns can be found across the 1 dB gain bandwidth.
关键词： stable gain,aperture coupled,magneto-electric dipole,wideband
更新于2025-09-23 15:21:01
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Electric dipole of InN/InGaN quantum dots and holes and giant surface photovoltage directly measured by Kelvin probe force microscopy
摘要： We directly measure the electric dipole of inn quantum dots (QDs) grown on in-rich inGan layers by Kelvin probe force microscopy. This significantly advances the understanding of the superior catalytic performance of inn/inGan QDs in ion- and biosensing and in photoelectrochemical hydrogen generation by water splitting and the understanding of the important third-generation inGan semiconductor surface in general. the positive surface photovoltage (SpV) gives an outward QD dipole with dipole potential of the order of 150 mV, in agreement with previous calculations. After HCl-etching, to complement the determination of the electric dipole, a giant negative SpV of ?2.4 V, significantly larger than the inGan bandgap energy, is discovered. this giant SpV is assigned to a large inward electric dipole, associated with the appearance of holes, matching the original QD lateral size and density. Such surprising result points towards unique photovoltaic effects and photosensitivity.
关键词： electric dipole,Kelvin probe force microscopy,surface photovoltage,inn/inGan quantum dots,photovoltaic effects
更新于2025-09-23 15:21:01
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<i>Ab initio</i> study of parity and time-reversal violation in laser-coolable triatomic molecules
摘要： Electronic structure enhancement factors of simultaneous parity and time-reversal violation (P, T violation) caused by an electric dipole moment of the electron (eEDM) and scalar-pseudoscalar nucleon-electron current (SPNEC) interactions are reported for various metal monohydroxides, several of which are considered laser-coolable and promising candidates for an eEDM measurement. Electronic structure enhancements are calculated ab initio within zeroth-order regular approximation (ZORA) for CaOH, SrOH, BaOH, RaOH, and YbOH. Scaling behavior with respect to nuclear charge numbers and the ratio of enhancement factors for both discussed sources of P, T violation are analyzed, which are crucial to obtaining stringent bounds on parameters for new physics from experiments.
关键词： laser-coolable molecules,electric dipole moment,ab initio calculation,scalar-pseudoscalar nucleon-electron current,parity and time-reversal violation,ZORA
更新于2025-09-23 15:21:01
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Hole spin in tunable Ge hut wire double quantum dot
摘要： Holes in germanium (Ge) exhibit strong spin-orbit interaction, which can be exploited for fast and all-electrical manipulation of spin states. Here, we report transport experiments in a tunable Ge hut wire hole double quantum dot. We observe the signatures of Pauli spin blockade (PSB) with a large singlet-triplet energy splitting of ~1.1 meV and extract the g factor. By analyzing the the PSB leakage current, we obtain a spin-orbit length ?????? of ~ 40–100 nm. Furthermore, we demonstrate the electric dipole spin resonance. These results lay a solid foundation for implementing high quality tunable hole spin-orbit qubits.
关键词： Pauli spin blockade,electric dipole spin resonance,germanium,spin-orbit interaction,quantum dots
更新于2025-09-23 15:19:57
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A Circularly-Polarized Differentially-Fed Transmission-Line-Excited Magneto-Electric Dipole Antenna Array for 5G Applications
摘要： A differentially-fed circularly-polarized magneto-electric dipole (ME-dipole) array is proposed for 5G applications. The proposed transmission-line-excited (TLE) antenna, fabricated on a printed-circuit-board (PCB), can achieve wide impedance and axial ratio (AR) bandwidths and high gain. The antenna consists of a 2×2 ME-dipole array enclosed by a circular cavity. It is modified from our previous work on linearly-polarized (LP) array with its element orientation selectively rotated by ±45o with respect to the differentially-fed transmission line and the use of sequential rotation technique (SRT) to generate circularly-polarized (CP) radiation. A differential feed network is utilized to feed the prototype for experiments. Experiments show that the antenna can present an overlapping impedance and AR bandwidth of 32.2% from 52.2 to 72.2 GHz with a broadside left-handed CP (LHCP) gain from 10.2 to 11.8 dBic. The proposed CP antenna retains all the salient features of our previously proposed linearly-polarized (LP) antenna in symmetric and stable radiation patterns and relatively low back radiation levels.
关键词： fifth generation (5G),Circularly-polarized (CP),magneto-electric dipole (ME-dipole),differential feed
更新于2025-09-19 17:15:36
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Laser-Cooled Polyatomic Molecules for Improved Electron Electric Dipole Moment Searches
摘要： Doppler and Sisyphus cooling of 174YbOH are achieved and studied. This polyatomic molecule has high sensitivity to physics beyond the Standard Model and represents a new class of species for future high-precision probes of new T-violating physics. The transverse temperature of the YbOH beam is reduced by nearly two orders of magnitude to < 600 μK and the phase-space density is increased by a factor of > 6 via Sisyphus cooling. We develop a full numerical model of the laser cooling of YbOH and ?nd excellent agreement with the data. We project that laser cooling and magneto-optical trapping of long-lived samples of YbOH molecules are within reach and these will allow a high sensitivity probe of the electric dipole moment (EDM) of the electron. The approach demonstrated here is easily generalized to other isotopologues of YbOH that have enhanced sensitivity to other symmetry-violating electromagnetic moments.
关键词： polyatomic molecules,electron electric dipole moment,laser cooling,Sisyphus cooling,YbOH
更新于2025-09-19 17:13:59