Splitting Of Atomic Levels Research Articles

Study of the influence of gamma irradiation on ferrite-spinel monocrystals

The mechanisms of redistribution of metal ions and the formation of defects in ferrite spinel upon irradiation are complex and depend on a number of factors. Therefore, computer simulations and experimental studies are important for understanding the behavior of the physical properties of these materials under the influence of radiation. The development of new materials that can withstand radiation damage is of great importance for a range of applications, including solid state physics, nuclear physics, space research and medical applications. In this work, the effect of gamma irradiation on Co0,75Cu0,25Fe2O4 ferrite single crystals has been investigated. An earlier study using Mössbauer spectroscopy was carried out to determine the changes in the metal ion content in the sublattices of ferrite spinels. These changes affect the magnetic crystallographic anisotropy of the material [1]. Data can be found in the scientific literature that indicate that gamma irradiation leads to changes in the magnetic susceptibility of materials and to changes in the magnetization curve [2,3]. These changes in physical properties can be explained by redistribution of metal ions in octahedral and tetrahedral sublattices, since metal ions in sublattices have splitting of atomic levels.

Atomic-level-mixing contribution to the P,T -odd Faraday effect as an enhancement factor in the search for P,T -odd interactions in nature

Recently, a $\mathcal{P},\mathcal{T}$-odd Faraday effect (PTFE), optical rotation in an external electric field parallel to the light propagation direction, was discussed as a promising tool for observation of the electron electric dipole moment in the intracavity absorption spectroscopy with atoms or molecules. The main mechanism leading to this effect, the linear Stark splitting of atomic levels (PTFE, LS) is well known. This mechanism is similar to the Zeeman splitting mechanism in case of the ordinary Faraday effect, i.e., optical rotation in an external magnetic field. In this paper we analyze the other possible mechanisms of PTFE, in particular, the atomic-level-mixing mechanism (PTFE, LM). In our analysis we perform considering PTFE (as well as the ordinary FE) as a kind of electro- (magneto-) optical circular birefringence. For the ordinary FE the level-mixing mechanism (FE, LM) is known apart from the main Zeeman level splitting mechanism (FE, LS). However, (PTFE, LM) mechanism for the PTFE was never considered in literature. Usually, the (FE, LS) mechanism dominates and the same was expected for (PTFE, LS). We demonstrate, however, that with heavy diatomic molecules, in particular in PbF, the contribution of (PTFE, LM) may essentially exceed the (PTFE, LS). This promises an additional enhancement of $\mathcal{P},\mathcal{T}$-odd effects in experiments with PbF molecule and makes this molecule one of the best candidates for performing such experiments.

Features of the Angular Distribution of Light Scattered by a Cold Atomic Ensemble Placed in a Static Electric Field

The angular distribution of light scattered by a cold atomic ensemble placed in an external electric field is investigated analytically. It is shown that the Stark splitting of atomic levels substantially modifies the character of multiple scattering and, in particular, the effect of coherent backscattering of light. The possibility of using the described approaches in the diagnostics of magnetic nanofluids and perfect optical crystals is discussed.

Specific Features of Interatomic Dipole–Dipole Interaction near a Perfectly Conducting Charged Surface

Specific features of dipole–dipole interaction between two motionless point atoms located near a perfectly conducting charged plate are investigated theoretically within a consistent quantum microscopic approach. These features are analyzed on the basis of the dynamics of cooperative spontaneous decay of excited states of a diatomic quasimolecule. The decay rate is investigated as a function of the interatomic distance, the orientation angle of the quasimolecule with respect to the plane of the plate, and the distance between the quasimolecule and the plate. It is shown that the conducting plate significantly modifies the character of dipole–dipole interaction even when the plate is not charged. When the plate is charged, the Stark splitting of atomic levels leads to an additional modification of the interatomic interaction. The features observed are explained on the basis of the analysis of the spectrum of collective states of diatomic molecules.

Calculating Spectral Characteristics of the Helium Atom Excited by an Electric Field in Plasma of Current Sheets

In this work, the behavior of the energy spectrum and probabilities of transitions between the Stark states are studied theoretically for the helium spectrum emitted by plasma of current sheets. Calculations are performed by the method of the energy matrix diagonalization of an atom in the electric field. The results obtained have allowed us to reveal a number of regularities in the behavior of shifts and splitting of atomic levels and transition probabilities for the emission spectrum of the helium atom in a circularly polarized electric field arising in plasma of current sheets.

Band gap in graphene induced by vacuum fluctuations

The electrons in undoped graphene behave as massless Dirac fermions. Therefore graphene can serve as an unique condensed-matter laboratory for the study of various relativistic effects, including quantum electrodynamics (QED) phenomena. Although theoretical models describing electronic properties of graphene have been elaborated in details, the QED effects were usually neglected. In this paper we demonstrate theoretically that QED can drastically modify electronic properties of graphene. We predict the following QED effect - the opening of the band gap in a graphene monolayer placed inside a planar microcavity filled with an optically active media. We show that this phenomenon occurs due to the vacuum fluctuations of the electromagnetic field and is similar to such a well-known phenomenon as a vacuum-induced splitting of atomic levels (the Lamb shift). We estimate the characteristic value of the band gap and find that it can sufficiently exceed the value of the Lamb shift.

Cavity QED with cold atoms trapped in a double-well potential

We investigate the interplay dynamics of a cavity QED system, where the two-level atoms are trapped in a double-well potential, and the cavity mode, with a frequency largely detuned from the atomic level splitting, is driven by a probe laser. The interaction between the center-of-mass motion of the atoms and the cavity mode is induced by the position-dependent atom-field coupling. The dynamics of the system is characterized by two distinct time scales, the inverse of the atomic interwell tunneling rate and the inverse of the cavity loss rate. The system shows drastically different (quasi)steady behaviors in the short- and long-time intervals, and the detection of the statistics of atom number distribution from the transmission spectra is available only in the short-time interval.

Dispersion properties of electromagnetically induced transparency under the Doppler broadening

The influence of heat motion of atoms in gaseous media on the features of manifestation of electromagnetically induced transparency is investigated. Taking into account elastic and inelastic collisions, fairly general and compact analytical relations are derived for the absorption and refraction coefficients of the probe wave in the presence of high-power inducing radiation, resonant to the adjacent atomic transition. It is shown, that occurrence of narrow resonance structures in the Doppler absorption and refraction profile is due to “overlap” of effective resonance velocities of atoms. The atomic level splitting in the strong wave field is uniformly analyzed in the entire intensity range. Interference transparency in a particular region of the Doppler profile is found to be accompanied by high resonance dispersion of the refraction coefficient, which is important for generating slow radiation and controlling its parameters.

Higher order diamagnetic contributions to shift and splitting of atomic levels in a magnetic field

The contributions of the diamagnetic interaction to the magnetic field-induced shift and splitting of atomic levels in the first and second orders of perturbation theory are calculated. The tensor of the second-order diamagnetic susceptibility for a degenerate state of atom, chi (2)nlm, is decomposed into irreducible parts by analogy to the electric hyperpolarizability. The irreducible parts are written in terms of the second-order radial matrix elements of the quadrupolar operator. Numerical calculations have been carried out for the ground and excited states of alkali atoms. For the states of the hydrogen atom with the highest angular momenta, l=n-1, l=n-2, and projections on the field vector m=+or-1, +or-(l-1) (the nondegenerate states), the analytic expressions for the second-order diamagnetic susceptibilities, chi (2)nlm, have been derived, providing the information on the asymptotic behaviour of chi nlm for the high-momentum Rydberg states with n>>1. The boundaries, for the use of perturbation theory in the calculation of atomic energy in strong magnetic fields, are also discussed.

Squeezing-enhanced and -reduced atomic-level splitting in two-photon dynamics.

In this paper, the two-photon Bloch equations of a two-level atom in broadband squeezed light are derived. On this basis, we discuss two-photon dynamic Stark splitting of atomic levels and the time evolution of atomic variables. The phenomena of squeezing-induced enhancement and reduction of dynamic Stark splitting of the atomic levels and overdamping of atomic time evolution are obtained.

Resonance interaction of intense light with atoms

Some typical resonance nonlinear-optics phenomena taking place when light interacts with atoms are considered. The multitude of such phenomena reduces to scattering of the perturbing light, perturbation of the atomic spectrum, excitation of an atom and its ionization. In all these cases the investigations are carried out using the simplest model—an isolated atom in a monochromatic external field. Such a model enables one to give an exact description of many elementary processes. On the other hand it is sufficiently realistic. A detailed investigation is carried out of resonance fluorescence, spontaneous Raman scattering, multiphoton excitation of atoms, resonance shifts and splitting of atomic levels and resonance lonication of atoms. The nature of these processes is investigated as a function of the intensity of the external field, its frequency, a specific atomic spectrum, the nature of polarization of the perturbing field, and the degree of its nonlinearity. The role played by the field of the electromagnetic vacuum is analyzed. Theoretical predictions are compared with the results of many experiments describing resonance processes of the interaction of an intense light field with atoms.

Atomic level splitting by external fields

We present in this paper an explanation, based on the properties of the Racah operators and the Wigner coefficients, of a set of rules which have been recently proposed for the solution of the quantitative problem of the splitting of a degenerate level.