Arbitrary Mutual Orientation Research Articles

Strong radiative coupling between two quantum emitters with arbitrary mutual orientation via a silver nano-arc

Strong radiative coupling realizes coherent exchange of single excitation between two quantum emitters, while their dipole orientation influences the coupling strength in anisotropic environments. We propose a silver nano-arc with arbitrary radian which can support two hot spots of electric field with radian-independent resonant wavelength. Two quantum emitters resonant with the cavity mode, embedded inside the two hot spots and oriented along the nano-arc axis, can realize strong radiative coupling, verified by the large splitting and anti-crossing behavior in the spectrum and the population oscillation in the time domain. All these signatures of strong radiative coupling are robust against the nano-arc’s curvature. Our work provides a flexible approach to realize strong radiative coupling between two quantum emitters with arbitrary mutual orientation and facilitates quantum information processing.

Ultra-high energy collisions in static space-times: single versus multi-black hole cases

We consider collision of two particles near static electrically charged extremal black holes and elucidate the conditions under which the energy in the centre of mass frame \(E_{c.m.}\) grows unbounded. For a single black hole, we generalize the results obtained earlier for the Reissner–Nordström metric, to distorted black holes. In the multi-black hole space-time, qualitatively new features appear. If the point of collision is close to at least two horizons simultaneously, unbounded \(E_{c.m.}\) are possible (i) without fine-tuning of particles’ parameters, (ii) for an arbitrary mutual orientation of two velocities. Such a combination of properties (i) and (ii) has no analogues in the single black hole case and facilitates the condition of getting unbounded \(E_{c.m.}\). Collisions in the electro-vacuum Majumdar–Papapetrou metric (several extremal black holes in equilibrium) is analyzed explicitly.

Acoustic wave propagation in uniform glow discharge plasma at an arbitrary angle between the electric field and wave vectors

This paper extends the recently reported one-dimensional model for sound propagation in glow discharge plasma to arbitrary mutual orientation of the plasma electric field and acoustic wave vectors. The results demonstrate that an acoustic wave in plasma may amplify, attenuate, or remain unchanged depending on the angle between these vectors and on the power input into the discharge. Quantitative evaluations indicate that for glow discharge plasma of a self-sustained discharge in air at the electric current densities of the order of 100 mA cm−2, a gain of as much as 1 m−1 at 0° angle between the vectors changes to similar strength attenuation for the 90° angle.

Oscillator strength spectrum of hydrogen in strong magnetic and electric fields with arbitrary mutual orientation

We present oscillator strength spectra of the hydrogen Balmer $\ensuremath{\alpha}$ series in crossed strong magnetic and electric fields. Field strength regimes of interest ($\ensuremath{\gamma}\ensuremath{\le}0.02\phantom{\rule{0.3em}{0ex}}\mathrm{a}.\mathrm{u}.$ and $F\ensuremath{\le}1\ifmmode\times\else\texttimes\fi{}{10}^{8}\phantom{\rule{0.3em}{0ex}}\mathrm{V}∕\mathrm{m}$) are the characteristic strengths observed on the surface of white dwarf stars. Based on the pseudospectral discretization technique, two independent methods have been developed to achieve reliable oscillator strengths in crossed fields. The effect of relative orientation between the magnetic and electric fields is clarified. Compared to the parallel configuration, we have observed that for the field strength regimes of interest, the perpendicular component of electric fields only results in a weaker coupling between the states belonging to the different subspaces of magnetic quantum numbers. This observation explains why the spectrum of oscillator strengths in crossed electric and magnetic fields with arbitrary mutual orientation shows similar behavior compared to that in parallel fields. However, a careful analysis shows that the two stronger transition lines at $5546$ and $5620\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ previously attributed to the Balmer $\ensuremath{\alpha}$ series are now identified to belong to the Balmer $\ensuremath{\beta}$ series. An effective scheme has also been suggested to calculate the bound-free opacities of hydrogen atoms in crossed fields.

Investigating the hydrogen atom in crossed external fields by the method of moments

Recurrence relations of perturbation theory for hydrogen ground state are obtained. With their aid polarizabilities in constant perpendicular electric and magnetic fields are computed up to 80th order. The high orders asymptotic is compared with its quasiclassical estimate. For the case of arbitrary mutual orientation of external fields a general sixth order formula is given.

Screened electrostatic interactions between clay platelets

An effective pair potential for systems of uniformly charged lamellar colloids in the presence of an electrolytic solution of microscopic co- and counterions is derived. The charge distribution on the discs is expressed as a collection of multipole moments, and the tensors which determine the interactions between these multipoles are derived from a screened Coulomb potential. Unlike previous theoretical studies of such systems, the interaction energy may now be expressed for discs at arbitrary mutual orientation. The potential is shown to be exactly equivalent to the use of linearized Poisson–Boltzmann theory.

Supermatrix approach to polarized neutron reflectivity from arbitrary spin structures

The general equation for polarized neutron reflectivity is derived and presented in an invariant vector form that is independent of the selection of a specific coordinate system. Using this representation the reflectivity may easily and thoroughly be analyzed for arbitrary orientation of the sample, the incident beam polarization, and the direction of polarization analysis. It is shown that the complete information that can be extracted from experimental data by a detailed polarization analysis is given by the following quantities: the two complex eigenvalues of the reflectance matrix and a complex vector defining a direction that coincides with the direction of the magnetizations in a collinear magnetization arrangement, but depends on the momentum transfer in the general noncollinear case. A supermatrix formalism is developed and illustrated that allows us to calculate these parameters for multilayers with arbitrary mutual orientation of the magnetizations in individual layers. Our approach opens an alternative way to a complete and unambiguous characterization of artificial magnetic structures of high complexity.

Hydrogen atom in very strong magnetic and electric fields.

We solved the three-dimensional Schr\odinger equation for a hydrogen atom in strong magnetic and electric fields of arbitrary mutual orientation, obtaining accurate values for the wavelengths and oscillator strengths of some low-lying bound-bound transitions. The influence of the electric-field strength and its relative orientation to the magnetic field on the calculated spectra is compared with the diamagnetic hydrogen atom. We therefore focus on field strengths relevant to the interpretation of spectra of magnetic white dwarf stars---one of the major applications of these calculations. \textcopyright{} 1996 The American Physical Society.

Three-dimensional hydrogen atom in crossed magnetic and electric fields.

We give a solution of the three-dimensional Schr\"odinger equation for the electron of a hydrogen atom in external electric and magnetic fields of arbitrary mutual orientation. The rearrangement of the energy spectrum due to changing in the mutual orientation of the fields is evaluated by using the n=2 multiplet as an example. The calculations agree with second-order perturbation formulas that exist for the special cases of mutually parallel and orthogonal fields. For another special two-dimensional case which is currently being extensively investigated, namely, the hydrogen atom in a strong magnetic field, our approach agrees with calculations by other authors and yields more accurate binding energies for certain low-lying excited states that have been considered.

The hydrogen atom in crossed static electromagnetic and non-resonant laser fields

The energy splittings and wave function of a hydrogen atom in crossed uniform static electromagnetic and non-resonant monochromatic electric fields of arbitrary mutual orientation are obtained within the "one-shell" approximation. The intensities of the Lyman lines are also obtained. A special analytical method is used. Relativistic corrections and spin-orbit interactions are not considered.

Determination of the asymmetry parameter of the electric field gradient tensor for nuclei with spin I= [formula omitted] from the echo envelope shape in powders

The calculation of the echo envelope shape In powders containing nuclei with I= 3 2 was carried out for an arbitrary mutual orientation of the external fields and for any values of η. As a result of computer processing of the expression obtained for the situation in which the radiofrequency field is aligned parallel to the static magnetic field the relations between η and experimentally measured parameters were obtained. These relationships make possible the determination Value of η for nuclei with I= 3 2 in powders.