Electric Dipole Oscillator Research Articles

Photon angular momentum and zero-point oscillations

Abstract Radiation from certain oscillating charge distributions can have angular momentum that cannot be
explained in classical electrodynamics. We consider the angular momentum of a single-photon field
from an electric dipole oscillator and in particular compare the classical and quantum expressions
for the mean-square field angular momentum. We show that differences in these expressions are
attributable to zero-point oscillations of unexcited states of the dipole oscillator.

Entropy Considerations in Stochastic Electrodynamics

The use of entropy concepts in the field of stochastic electrodynamics is briefly reviewed here. Entropy calculations that have been fully carried out to date are discussed in two main cases: first, where electric dipole oscillators interact with zero-point, or zero-point plus Planckian, or Rayleigh–Jeans radiation; and second, where only these radiation fields exist within a cavity. The emphasis here is on the first, more complicated, case, where both charged particles and radiation fields are present and interacting. Unlike the usual exposition on entropy in classical statistical mechanics, involving probabilistic notions of phase-space occupation, the calculations to date for both particles and fields, or for fields alone, follow the caloric entropy method, where the notions of heat flow, adiabatic surfaces, and isothermal conditions are utilized. Probability notions certainly still enter into the calculations, as the fields and charged particles interact stochastically together, following Maxwellian electrodynamics. Examples of phase-space calculations for harmonic oscillators and classical hydrogen atoms are carried out, emphasizing how much farther caloric entropy calculations have successfully gone.

Spin-induced linear polarization of photoluminescence in antiferromagnetic van der Waals crystals.

Antiferromagnets are promising components for spintronics due to their terahertz resonance, multilevel states and absence of stray fields. However, the zero net magnetic moment of antiferromagnets makes the detection of the antiferromagnetic order and the investigation of fundamental spin properties notoriously difficult. Here, we report an optical detection of Néel vector orientation through an ultra-sharp photoluminescence in the van der Waals antiferromagnet NiPS3 from bulk to atomically thin flakes. The strong correlation between spin flipping and electric dipole oscillator results in a linear polarization of the sharp emission, which aligns perpendicular to the spin orientation in the crystal. By applying an in-plane magnetic field, we achieve manipulation of the photoluminescence polarization. This correlation between emitted photons and spins in layered magnets provides routes for investigating magneto-optics in two-dimensional materials, and hence opens a path for developing opto-spintronic devices and antiferromagnet-based quantum information technologies.

Probability Calculations Within Stochastic Electrodynamics

Several stochastic situations in stochastic electrodynamics (SED) are analytically calculated from first principles. These situations include probability density functions, as well as correlation functions at multiple points of time and space, for the zero-point (ZP) electromagnetic fields, as well as for ZP plus Planckian (ZPP) electromagnetic fields. More lengthy analytical calculations are indicated, using similar methods, for the simple harmonic electric dipole oscillator bathed in ZP as well as ZPP electromagnetic fields. The method presented here makes an interesting contrast to Feynman’s path integral approach in quantum electrodynamics (QED). The present SED approach directly entails probabilities, while the QED approach involves summing weighted paths for the wave function.

Simultaneous epsilon-negative and mu-negative property of Ni/CaCu3Ti4O12 metacomposites at radio-frequency region

Metacomposites with simultaneous epsilon-negative and mu-negative property have drawn tremendous attentions due to their promising applications in electromagnetic field. Herein, Ni/CaCu3Ti4O12 (Ni/CCTO) metacomposites were prepared by low-temperature pressureless sintering method. It was observed that Ni chains were gradually interconnecting to each other with increasing Ni content, and a percolation behavior was observed. Epsilon-negative property was obtained above percolation threshold attributing to the synergistic effect of induced electric dipole and low-frequency plasma oscillation in Ni networks, which was explained by the superposition of Drude and Lorentz model. Mu-negative property was observed above ∼34 MHz and ∼120 MHz for 60 wt% and 70 wt% Ni/CCTO composites respectively, which may originate from the combined effects of diamagnetic response, domain wall motion and gyromagnetic spin rotation. Hence, simultaneous epsilon-negative and mu-negative property at radio-frequency region was realized in Ni/CCTO metacomposites. Besides, the composites presented hopping conduction behavior, and then changed into metal-like conduction behavior with increasing Ni content. The impedance response of Ni/CCTO composites clarified the correlation between epsilon-negative and inductive character. This work could broaden the scope of metacomposites and pave its way to potential applications of electromagnetic shielding, novel antenna, and high-k capacitors.

Energy levels, wavelengths, and transition probabilities for transitions in Pd XLII

Energy levels and lifetimes for the lowest 204 fine-structure levels belonging to the 2s22p, 2s2p2, 2p3, 2s23l, 2s2p3l, 2p23l, 2s24l, 2s2p4l, and 2p24l (l = s, p, d, f) configurations of B-like Pd XLII are calculated using the multiconfiguration Dirac-Hartree-Fock (MCDHF) method, as well as wavelengths, transition probabilities, weighted oscillator strengths, and line strengths for electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2) transitions among these levels. In the calculations, the contributions from Breit interaction and quantum electrodynamics (QED) corrections are taken into account. Comparisons are made with available theoretical energies and electric dipole oscillator strengths.

Investigation of Li2O–Gd2O3–MO–B2O3–Nd2O3 (MO=Ba/Bi) glasses for laser applications by Judd–Oflet (J–O) theory

In this work, we synthesize Li2O–Gd2O3-MO-B2O3–Nd2O3 glasses (where MO = Ba/Bi) by melt-quenching technique for laser applications; characterize their physical properties, absorption and luminescence spectra; and determine their decay time and Judd-Oflet (J-O) parameters. We confirm the glass phase of the samples by XRD pattern and obtain the J-O parameters for Nd3+ in the glasses from the absorption and photoluminescence emission spectra, while measuring the intensity of the electric dipole transitions and oscillator strengths from absorption spectra and the radiative parameters from photoluminescence emission spectra. We also determine some key parameters of the laser materials, such as radiative decay time, quantum efficiency and stimulated emission cross section. The lifetime decreases with increasing Nd3+ concentration that is indicative of energy transfer between Nd3+ ions. We also demonstrate that the physical properties and absorption spectra are independent of the gadolinium ions (Gd2O3), while the luminescence properties are functions of the Gd2O3 due to the efficient energy transfer from the Gd3+ ions to the incorporated activator (Nd3+). These results suggest that the 50Li2O-15Gd2O3–5Bi2O3-28.5B2O3-1.5Nd2O3 glass is useful for laser applications at 577-nm excitation and at 1.07-μm emission.

Electric dipole oscillation in solids characterized by Fourier transform extreme ultraviolet attosecond spectroscopy

We characterized electronic dipole oscillations in chromium doped sapphire (Cr:Al2O3) using Fourier transform extreme ultraviolet attosecond spectroscopy (FTXUV) combined with an isolated attosecond pulse, which reveals the electric band-structure and dephasing process in solids.

Relativistic calculations on the x-ray satellites of platinum with multiply ionized L shell

The energies, electric dipole rates and oscillator strengths of Kα x-ray satellites from 1s–2p transitions in platinum with a single vacancy in the K shell and variously ionized L shell are calculated using multi-configuration Dirac Fock wavefunctions with the inclusion of Breit interaction and quantum electrodynamics effects. The computations have been performed for low ionized (Pt1+–Pt6+) and also for highly ionized (Pt69+–Pt77+) Pt. As Kα x-ray satellites with spectator vacancies only in the L shell, to the best of our knowledge, have been studied for the first time, to check the accuracy of the present work, calculations have also been performed for H-, He-, Li-, Be-, B- and F-like Pt for which theoretical data for comparison exist. The purpose of choosing a high Z element is that the detailed decay properties of heavy ions due to systematic 1s–2p transitions with spectator vacancies in the L shell using fully relativistic treatment are unexplored and the increasing need for reliable data from such ions in various applications that are under investigations in recent years. Also, for heavy ions like Pt, the contribution from the competing non-radiative transitions is less and hence the atomic properties are largely due to radiative transitions. The K X ray satellite energies, rates and resonance photo- ionization cross sections from H-, He-, Li-, Be-, B- and F-like Pt are compared with available data.

Transition probabilities of Er3+ ions in alumino-silicate glasses

The spectroscopic properties of Er-doped Ca3Al2Si3O12 and Mg3Al2Si3O12 glasses produced by the Laser Floating Zone technique are presented in this work. By measuring the absorption spectra and refractive index dispersion of the materials, JO parameters of the Er3+ ions have been obtained in both doped materials, where very good accordance between the experimental and theoretical electric dipole oscillator strengths is found. Using calculated electric and magnetic dipole strengths, the branching ratios of the different optical transition of Er3+ in Ca and Mg glasses have been obtained, where the radiative lifetime of each level has been also calculated. The experimental lifetimes of the 4S3/2, 4I11/2 and 4I13/2 manifolds have been measured under pulse excitation. These values have been related with the radiative lifetime calculated by the JO analysis, allowing to determine the non-radiative probabilities of the levels. In addition, a gap law has been established for both Ca and Mg alumino-silicate glasses. Finally, the covalency of the Er-O bond was studied in terms of the spectroscopic features of these glasses.

Multi-petahertz electron interference in Cr:Al2O3 solid-state material

Lightwave-field-induced ultrafast electric dipole oscillation is promising for realizing petahertz (1015 Hz: PHz) signal processing in the future. In building the ultrahigh-clock-rate logic operation system, one of the major challenges will be petahertz electron manipulation accompanied with multiple frequencies. Here we study multi-petahertz interference with electronic dipole oscillations in alumina with chromium dopant (Cr:Al2O3). An intense near-infrared lightwave-field induces multiple electric inter-band polarizations, which are characterized by Fourier transform extreme ultraviolet attosecond spectroscopy. The interference results from the superposition state of periodic dipole oscillations of 667 to 383 attosecond (frequency of 1.5 to 2.6 PHz) measured by direct time-dependent spectroscopy and consists of various modulations on attosecond time scale through individual electron dephasing times of the Cr donor-like and Al2O3 conduction band states. The results indicate the possible manipulation of petahertz interference signal with multiple dipole oscillations using material band engineering and such a control will contribute to the study of ultrahigh-speed signal operation.

Oscillator strengths for spin-changing P–D transitions in He I including the effect of a finite nuclear mass and intermediate coupling

We have calculated the electric dipole (E1) oscillator strengths and spontaneous decay rates for 12 spin-changing P–D transitions of atomic helium. We included the effects of the finite nuclear mass and the anomalous magnetic moment of the electron. The specific transitions for 4He are [Formula: see text] and [Formula: see text] with n = 2, 3, 4 and n′ = 3, 4. To include the effects of intermediate coupling between pure LS and jj, we used the Breit formulation for the spin–orbit and spin–other-orbit operators and combined the results of the exact diagonalization of the 2 × 2 energy matrix with pseudostate expansions to perform the perturbation sums over intermediate states. We calculated both the length and velocity gauges as a check on numerical accuracy and the validity of the transition operators.

Mechanism of equivalent electric dipole oscillation for high-order harmonic generation from grating-structured solid-surface by femtosecond laser pulse

We theoretically study high-order harmonic generation (HHG) from relativistically driven overdense plasma targets with rectangularly grating-structured surfaces by femtosecond laser pulses. Our particle-in-cell (PIC) simulations show that, under the conditions of low laser intensity and plasma density, the harmonics emit principally along small angles deviating from the target surface. Further investigation of the surface electron dynamics reveals that the electron bunches are formed by the interaction between the laser field and the target surface, giving rise to the oscillation of equivalent electric-dipole (OEED), which enhances specific harmonic orders. Our work helps understand the mechanism of harmonic emissions from grating targets and the distinction from the planar harmonic scheme.

Oscillator strengths for 1s2 1S0–1s2p 3P1,2 transitions in helium-like carbon, nitrogen and oxygen including the effects of a finite nuclear mass

We have calculated the electric dipole (E1) and magnetic quadrupole (M2) oscillator strengths and spontaneous decay rates for the spin-changing transitions of helium-like C v, N vi and O vii. We added the effects of the finite nuclear mass and the anomalous magnetic moment of the electron including an extra term derived by Pachucki. For the E1 calculations we used the Breit approximation and pseudostate expansions to perform the perturbation sums over intermediate states in both the length and velocity gauge as a check on numerical accuracy and the validity of the transition operators. There is some cancellation in the corrections for the nuclear mass and the electron anomaly so that if one is included the other should not be ignored

Sturmian bases for two-electron systems in hyperspherical coordinates

We give a detailed account of an ab initio spectral approach for the calculation of energy spectra of two active electron atoms in a system of hyperspherical coordinates. In this system of coordinates, the Hamiltonian has the same structure as the one of atomic hydrogen with the Coulomb potential expressed in terms of a hyperradius and the nuclear charge replaced by an angle dependent effective charge. The simplest spectral approach consists in expanding the hyperangular wave function in a basis of hyperspherical harmonics. This expansion however, is known to be very slowly converging. Instead, we introduce new hyperangular Sturmian functions. These functions do not have an analytical expression but they treat the first term of the multipole expansion of the electron–electron interaction potential, namely the radial electron correlation, exactly. The properties of these new functions are discussed in detail. For the basis functions of the hyperradius, several choices are possible. In the present case, we use Coulomb–Sturmian functions of half integer angular momentum. We show that, in the case of H−, the accuracy of the energy and the width of the resonance states obtained through a single diagonalization of the Hamiltonian, is comparable to the values given by state-of-the-art methods while using a much smaller basis set. In addition, we show that precise values of the electric-dipole oscillator strengths for transitions in helium are obtained thereby confirming the accuracy of the bound state wave functions generated with the present method.

Applications to metal K pre-edges of transition metal dimers illustrate the approximate origin independence for the intensities in the length representation

ABSTRACTX-ray absorption spectroscopy (XAS) in the metal K pre-edge is a standard probe of electronic and geometric structure of transition metal complexes. Simulating the K pre-edge spectra requires contributions beyond the electric dipole, but if that term is non-zero, the second-order terms, e.g. electric quadrupoles, are no longer origin-independent. In the velocity representation, complete origin independence can be achieved by including all terms to the same order in the oscillator strength. Here, we implement that approach in the length representation and use it for restricted active space (RAS) simulations of metal K pre-edges of iron monomers and dimers. Complete origin independence is not achieved and the size of the remaining errors depends on the electric dipole oscillator strength and its ratio in length and velocity representations. The error in the origin independence is in the ANO basis sets two orders of magnitude smaller than the value of the individual contributions. For systems with strong electric dipole contributions, the errors are not significant within 3 Å from a metal centre, far enough to handle many multi-metal systems. Furthermore, we discuss the convergence of the multipole expansion, the possibility to assign spectral contributions, and the origin of negative absorption intensities.

Electric dipole transition probabilities, oscillator strengths, and lifetimes for Co16+

The electric dipole transition probabilities, oscillator strengths, and lifetimes for Co16+ have been calculated within the weakest bound electron potential model (WBEPM) theory using experimental energy levels and theoretical expectation values of orbital radii corresponding to those energy levels under the assumption of the LS coupling scheme. In the calculations both multiplet and fine structure transitions are studied. The present results are consistent with earlier results given in the literature. Moreover, some transition probability and oscillator strength values not existing in the literature are reported for the first time.

Research Of Carbon Fibre Absorbing Material Based On Impedance Matching

The carbon fibre has a good characteristic of electrical conductivity. When cut short and dispersed, it reacts as electric dipole or harmonic oscillator to radar wave. This paper blends the short carbon fibre with ethoxyline resin, and makes films by spraying the blend on prepreg which made by glass fibre and resin, then measures the EM parameters with the free-space method, and designs the low reflectivity absorbing material from 8GHz to 18GHz by matching impedance and calculating the reflectivity of multilayer films. Adjusting the kinds and quantities of matching layers can shift the absorbing frequency bands, and become better absorbing respective in X-band and Ku-band. The absorbing material samples are made by vacuumizing and heating method, and their reflectivity correspond to the designed result. The designing method and absorbing material made in this paper can be referred in engineering application.

Oscillator strengths and lifetimes for Cu I

Electric dipole oscillator strengths and lifetimes for Cu I have been calculated within the weakest bound electron potential model theory and the quantum defect orbital theory under the assumption of the LS coupling scheme. In the calculations, many transition arrays including both multiplet and fine-structure transitions are considered. The present results are consistent with earlier theoretical calculations and experimental measurements. Some of these results are reported for the first time.

Controlling of spectral and optical parameters of the F8T2 liquid–crystalline polymer (LCP) by molarity for optoelectronic devices

In here, spectral and optical properties of the F8T2 polymer for different molarities were investigated by solution technique for optoelectronic applications. The interesting and useful results were obtained for optoelectronic applications. The absorption band of F8T2 polymer exhibits a vibronic structure with two peaks at 288 and 453nm due to π–π* electronic transition. The electronic spectra of the F8T2 can be characterized visible (Q) band and Soret (B) band. The significant spectral parameters such as absorption coefficient, molar extinction coefficient, mass extinction coefficients, electric dipole line strength and oscillator strength of the F8T2 polymer were calculated. The direct allowed band gap (Egd) and indirect allowed band gap (Egid) values (2.230 and 2.251eV, respectively) of the F8T2 polymer for 1.200μM are the highest values, while the Egd and Egid values (1.723 and 2.033eV, respectively) of the F8T2 for 9.460μM are the lowest values. The Egd values of the F8T2 polymer are lower than the Egid values. The real part of dielectric constant of the F8T2 polymer is composed normal and anomalous dispersion regions. F8T2 polymer can be used in the fabrication of many optoelectronic devices due to good soluble, spectral and optical properties.