Radiative properties of Zeeman components of atomic multiplets: Dependence of line intensities on the magnetic field

Analytical expressions for the dependence of the intensity of Zeeman components of doublet lines on the magnetic field are obtained. Sharp changes of these function on passing from the anomalous Zeeman effect to the Paschen-Back effect lead to the disappearance of marginal lines and the equalization of intensities of remaining lines. In the region of the complete Paschen-Back effect, a strong influence on these dependences is produced by the dynamic atom-field interaction, which weakens the paramagnetic effect in the states with a positive magnetic quantum number m and enhances the effect in the states with a negative m. Simple analytical expressions are obtained that take into account the effect of the diamagnetic interaction on line intensities. The role of the diamagnetic interaction increases in Rydberg atomic states with a large spin-orbit splitting. For the states with m > 0, it can lead to the “diamagnetic reversal” of the Paschen-Back effect, i.e., the recovery of the anomalous Zeeman effect.     

Nuclear magnetic shielding and diamagnetic susceptibility of interacting hydrogen atoms

A quantum-mechanical study is made of the changes of the nuclear magnetic screening constant σ and the diamagnetic susceptibility X of two interacting hydrogen atoms due to van der Waals and overlap interatomic forces (effects of electron spin being neglected). At large distances the calculations show that van der Waals forces decrease the nuclear screening but increase the diamagnetic susceptibility (in magnitude). As the internuclear distance is reduced the first effect of overlap forces is to increase the screening in the repulsive (electronic triplet) state but this is followed by a further reduction. Attractive overlap forces (as in the ground state of H₂) ultimately lead to an increase in screening.     

On levitation of diamagnetic bodies in a magnetic field

Various methods for calculating the force characteristics of a suspension ensuring levitation of diamagnetic bodies of various origin and shape are considered. The method of calculation is based on the computation of the energy of interaction of a body upon its displacement from the center of suspension for an arbitrary configuration of the suspending field. The method of quasi-homogeneous approximation is considered and compared with the method for calculating the force characteristics based on the general formula for the magnetic energy. The necessary and sufficient conditions for conservative stability of the equilibrium state are formulated, and the stability domain is determined. It is shown that the stability domain depends on the size of the body. Calculations of force characteristics are performed specifically for the suspension of a diamagnetic sphere. The dependences of forces and stiffnesses on the magnetic field strength are obtained, which makes it possible to analyze the stability of confinement of the diamagnetic sphere in the field of the system of circular currents.     

Radiative neutrino decay in a strong magnetic field

The radiative decay of neutrinos in a strong magnetic field that have relatively high energies, E ? m _e , is studied with allowance for positronium contribution to the photon polarization operator in the vicinity of the cyclotron resonance. It is shown that the probability for the process ν → νγ increases substantially upon taking into account the positronium contribution.     

Relativistic corrections to the energy levels of hydrogen atoms in a strong magnetic field

Relativistic corrections to the binding energies of various states of the strongly magnetized hydrogen atom are estimated by a perturbation calculation.     

抗磁和顺磁性材料在磁场中弱磁力实验测量

对抗磁性材料和顺磁性材料在强磁场中的弱磁力进行测量.利用设计的实验装置,成功测得抗磁性石墨片和顺磁性材料铝片在永磁铁阵列表面受到的弱磁力.研究证明弱磁力的大小与磁场及磁场梯度乘积成正比.     

Dependence of ultrasonic attenuation in semi-conductors on electric field strength

The dependence of the ultrasonic attenuation, or amplification, in semi-conductors on the electric field strength is derived. It is shown that the ultrasonic amplification does not increase linearly with the field, but, after reaching a maximum, it again decreases.     

Effect of diamagnetic substitutions in BaFe12O19 on the magnetic properties

The exchange parameters of BaFe₁₂O₁₉ have been calculated from the temperature dependence of the saturation magnetization using the molecular field theory. Under the assumption that the exchange parameters do not change for diamagnetic substitutions of the Fe³⁺ ions, it is shown that the temperature coefficient of the magnetization at room temperature cannot be decreased without decreasing the magnetization. Diamagnetic substitution in the octahedralf ₂ site would solely increase the saturation magnetization.     

Field-dependent diamagnetic transition in magnetic superconductor Sm1.85Ce0.15CuO4-y

The magnetic penetration depth of single crystal Sm(1.85)Ce(0.15)CuO(4-y) was measured down to 0.4 K in dc fields up to 7 kOe. For insulating Sm2CuO4, Sm3+ spins order at the Ne el temperature, T(N)=6 K, independent of the applied field. Superconducting Sm(1.85)Ce(0.15)CuO(4-y) (T(c) approximately 23 K) shows a sharp increase in diamagnetic screening below T(*)(H) which varied from 4.0 K (H=0) to 0.5 K (H=7 kOe) for a field along the c axis. If the field was aligned parallel to the conducting planes, T(*) remained unchanged. The unusual field dependence of T(*) indicates a spin-freezing transition that dramatically increases the superfluid density.     

Radiative properties of lanthanide and transition metal ions in nanocrystals

We examine the physical factors that influence the radiative transitions of small-radius optical centers in ellipsoidal nanoparticles. The main objective of this work is to reveal to the extent to which changes in the phonon subsystem and electron-phonon interaction caused by spatial confinement effects affect the radiative characteristics of optical centers in nanocrystals.     

Mott-Hubbard transition in a magnetic field

We study the density of states (DOS) as a function of the interaction U in the half-filled simplified Hubbard model in a magnetic field. This model is considered on the Bethe lattice in the limit of high dimensions. We show that the DOS can be calculated exactly, and that many of its properties have an astonishingly simple form. In particular, the DOS can be investigated explicitly in the limits of weak and strong coupling and near the metal-insulator transition. E.g., we find an explicit result for the critical value U_c, at which the metal-insulator transition occurs, as a function of the magnetization. The relation between the magnetization and the magnetic field is calculated numerically. An important result is that the metal-insulator transition, occurring in the model with B = 0, is continuously connected to the metal-insulator transition in the subspace of single spin flips.     

Lorentz ionization of atoms in a strong magnetic field

Lorentz ionization emerges due to the motion of atoms or ions in a strong magnetic field. We use the semiclassical approximation to calculate the probability w _L of Lorentz ionization. We also find the stabilization factor S, which takes into account the reduction by the magnetic field of the probability of ionization decay of the bound s state. We estimate the probabilities w _L in magnetic-cumulation experiments and in astrophysics. We also qualitatively examine the dynamics of the magnetic cumulation process with allowance for the conductivity of the shell. Finally, we discuss a paradox related to the use of the quasistationary solution at the shell expansion stage. Zh. éksp. Teor. Fiz. 115, 1642–1663 (May 1999)     

Radiative corrections to the Coulomb energy levels and emission of a hydrogen-like atom in a superstrong magnetic field

The probability and intensity of hydrogen-like atom emission in strong magnetic field В >> Z ^2α2 B ₀, α = e ²/cħ = 1/137, and B ₀ = m ² c ³ /eħ = 4.41⋅10¹³ G is calculated. The role of electron-positron vacuum polarization is discussed.     

Effect of a magnetic field on the ionization of atoms

The ionization probability of an atomic s state under the action of static electric and magnetic fields is calculated taking into account the Coulomb interaction between the escaping electron and the atomic core. The structure of the perturbation series for the energy of the level is investigated and the asymptotic behavior of the higher orders of the perturbation theory is found. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 6, 398–402 (25 March 1996)     

Nonclassical paths in the recurrence spectrum of diamagnetic atoms

Using time-independent scattering matrices, we study how the effects of nonclassical paths on the recurrence spectra of diamagnetic atoms can be extracted from purely quantal calculations. This study reveals an intimate relationship between two types of nonclassical paths: exotic ghost orbits and diffractive orbits. This relationship proves to be a previously unrecognized reason for the success of semiclassical theories, such as closed-orbit theory, and permits a comprehensive reformulation of the semiclassical theory that elucidates its convergence properties.     

Dependence of electron spin g-factor on magnetic field in quantum wells

The dependence of electron spin g-factor on magnetic field has been investigated in GaAs/AlGaAs quantum wells. We have estimated the electron g-factor from spin precession frequency in time-resolved photoluminescence measurements under a magnetic field in different configurations; the magnetic field perpendicular (g_⊥) and parallel (g_∥) to the quantum confinement direction. When the angle between the magnetic field and the confinement direction is 45°, we have found that g-factor varies depending on the direction of magnetic field and the circular polarization type of excitation light (σ⁺ or σ^?). These dependences of g-factor exhibit main features of Overhauser effect that nuclear spins react back on electron spin precession. The value of g_⊥ and g_∥ corrected for the nuclear effects agree well with the results of four-band k·p perturbation calculations.     

Radiative corrections in laser-dressed atoms: formalism and applications

The dressing of atomic states in a strong laser field modifies the structure of the incoherently scattered fraction of the laser intensity, which is described to a good approximation by the Mollow spectrum. The incoherent spectrum is generated by the fluctuations of the atomic dipole moment about its expectation value, and the positions of the peaks are approximately given by the energy differences between the dressed atomic energy levels. In this paper, we investigate radiative corrections received by the dressed states. Our calculations are motivated by the quest to understand in detail the interplay of a bound electron dressed by the highly populated laser mode and its interaction with the vacuum modes. Alternatively, this may be seen as an electron experiencing modified stimulated and spontaneous radiative corrections in a vacuum tailored by the laser field. We obtain dressed self-energy shifts that depend on the Rabi flopping frequency (and in turn on the laser intensity) and on the detuning of the laser field relative to the atomic resonance frequency. We find that the dressed radiative corrections differ in a nontrivial manner from the radiative shifts of the ‘bare’ atomic states.     

Phase transition properties for the kinetic Ising model in an oscillating magnetic field

The phase transition properties for the kinetic Ising model in a sinusoidally oscillating magnetic field are investigated by means of the mean-field calculations. The integrated phase diagrams for not only the amplitude of the oscillating field versus temperature but also the frequency of the oscillating field versus temperature have been calculated respectively, in which the discontinuous and continuous transitions are observed. Meanwhile the hysteresis loops in relation to the two kinds of the phase diagrams have been analyzed systematically, and the effects of the amplitude and the frequency of the oscillating field on the hysteresis loops are illustrated.