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.     

Two-quantum transitions between the fine-structure levels of a hydrogen-like atom

A study is made of the probability of two-quantum spontaneous transitions between fine-structure levels for fixed value of the principal quantum number (the radiation spectrum and the total transition probabilities are calculated) on the basis of the solution of the Dirac equation in a Coulomb field with arbitrary value of the charge of the nucleus.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 20–24, July, 1980.     

Relativistic correction for the Zeeman effect in a hydrogen-like atom

Based on an algebraic system of equations whose eigenvalues in the semirelativistic approximation determine the magnetic splitting of energy levels of two coupled Dirac particles with charges ±e and different masses, the splitting in extremely weak and weak magnetic fields is determined. In addition, a system of equations for charged particles with anomalous magnetic moments is given. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 3–13, December, 2006.     

Polarization of vacuum in a hydrogen-like relativistic atom: Hyperfine structure

An analysis is made of the contribution of the polarization of vacuum to the hyperfine splitting of the ground state of a hydrogen-like atom. An expression for the correction to the energy is obtained as an explicit function of the parameter Zα. The final expression derived in terms of generalized hypergeometric functions and their derivatives is a function of the particle mass ratio in orbit and in a vacuum loop, and is therefore valid for both ordinary and muonic atoms. Various asymptotic forms are also given.     

Perturbation of the excited states of the hydrogen atom and hydrogen-like ions by a neutral atom

Owing to the degeneracy of the energy levels, the wavefunction of the electron in the excited states of the hydrogen atom and hydrogen-like ions perturbed by a neutral atom B is significantly different from the wavefunction of the unperturbed state. The perturbed function has a wide high maximum in the region of atom B, which is explained by multiple collisions of the electron with atom B, because the classical trajectories in the Coulomb field are closed and the size of atom B is much smaller than the size of the excited-state orbit. The radiative lifetimes of the excited states are much larger than those of unperturbed states. The orbital angular momentum L of the excited electron is strongly changed in collisions with atom B owing to the quantum interference or mixing of the temporal phases of adiabatic wavefunctions. The cross sections for such a change in the orbital angular momentum are several orders of magnitude larger than the cross sections found in early investigations in the approximation of the single collision of the electron with atom B.     

Ionization of a single hydrogen-like atom by laser pulse of near-atomic strength

The dynamics of high-harmonic generation and atom ionization by a strong and superstrong laser field are studied. In contrast to many earlier works, the present theory does not impose limitations on the laser field’s strength. We solve the nonrelativistic problem of a single hydrogen-like atom’s ionization from the ground state by a short laser pulse of subatomic, atomic, and superatomic field strength. Within the framework of the proposed method, we investigated the matrix elements of the ionization transition and revealed its substantially nonlinear dependence on the laser field strength. Both ionization and recombination processes are taken into account. The proposed method enables us to take into account the arbitrary order multiphoton ionization processes.     

Stimulated emission from a single excited atom in a waveguide

We study stimulated emission from an excited two-level atom coupled to a waveguide containing an incident single-photon pulse. We show that the strong photon correlation, as induced by the atom, plays a very important role in stimulated emission. Additionally, the temporal duration of the incident photon pulse is shown to have a marked effect on stimulated emission and atomic lifetime.     

Photon emission from a two-level atom moving in a cavity

The interaction of a two-level atom uniformly moving along a classical trajectory with a high-Q cavity quantum mode is analyzed. The dressed-state method is used to derive a recurrence formula for the transition probability of the atom with photon emission; the temporal dynamics of this probability qualitatively depends on the Doppler shift of the atomic transition frequency, on the Rabi frequency of the atom-field system, and on the detuning of the atomic transition frequency from the field mode frequency. The emission dynamics of a moving atom is very sensitive to the detuning. Rabi-type oscillations with a frequency equal to the Doppler shift can arise under certain conditions. At resonance, the emission probability of a moving atom can considerably exceed the emission probability of an atom at rest. A plane-parallel-mirror cavity and a confocal spherical-mirror cavity are considered. It is shown that the peculiarities of Doppler-Rabi oscillations must be taken into account in micromaser theory.     

Emission of axions by a hydrogen-like atom in an ultrastrong magnetic field

The resonance effect of emission of axions by a hydrogen-like atom in an ultrastrong magnetic field B ≫ B ₀ = m ²/e = 4.41 × 10¹³ Gs, which is induced by polarization of electron-positron vacuum, is considered. The emission probability and the radiation intensity are on the order of (B/B ₀) × 10⁻¹² of electromagnetic radiation characteristics, which exceeds the conventional ratio by many orders of magnitude. It is shown that, at the temperature of early Universe ≲(Zα)² m, the contribution from the resonance mechanism prevails. However, the relation between the concentrations of relic photons and axions cannot explain the origin of cold dark matter. The axion energy density in “our epoch” is 10⁻⁴(B/B ₀) eV/cm³.     

Vacuum polarization in a hydrogen-like relativistic atom: g factor of a bound electron

The contribution of vacuum polarization to the g factor of a bound electron is considered for the ground state of a hydrogen-like atom. A final expression for the correction is obtained in terms of generalized hypergeometric functions and represents a function of parameter Zα and the ratio of the mass of the orbital particle (electron or muon) to the mass of a particle in the vacuum loop. Different asymptotic forms of this expression are derived for both common and muon atoms.     

Induced emission from a sodium Rydberg atom in a microwave cavity

Results are presented from an experiment on the observation of an induced microwave transition 37P-37S in sodium Rydberg atoms under the action of 30 thermal photons in a microwave cavity. The measured value of the transition rate (4±1.5)×10⁴ s⁻¹ agrees with the calculated value. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 6, 413–416 (25 March 1999)     

Three-dimensional atom localization via spontaneous emission in a four-level atom

We investigate high-precision three-dimensional (3D) atom localization in a coherently-driven, fourlevel atomic system via spontaneous emission. Space-dependent atom-field interactions allow atomic position information to be obtained by measuring spontaneous emission. By properly varying system parameters, atoms within a certain range can be localized with nearly a probability of 100% and a maximal resolution of ~0.04λ. This scheme may be useful for the high-precision measurement of the center-of-mass wave functions of moving atoms and in atom nanolithography.     

各向异性光子晶体中∧型原子的自发辐射性质

讨论了各向异性光子晶体中∧型三能级原子的辐射性质.研究发现,原子上能级与光子晶体带边的相对位置和两低能级相对位置将直接影响原子的动力学性质及其周围辐射场的性质.通过数值计算和理论分析,得到了光子晶体中原子周围辐射场在不同位置随时间演化的图像,并讨论了光子晶体对原子辐射谱的影响.     

Radio-frequency control of spontaneous emission from a coherently driven multilevel atom

The spontaneous emission properties of radio-frequency(RF)-driven multilevel atomic systems with three different configurations are investigated in details. It is demonstrated that, due to the presence of the RF-induced coherence in the multilevel system, a few interesting phenomena such as spectral-line narrowing, spectral-line enhancement, spectral-line suppression, and fluorescence-quenching can be realized under realistic experimental conditions. By inspecting single-RF-driven, double-RF-driven, and triple-RF-driven atomic systems, we find that (i) when only one RF-driven field is applied, there are two fluorescence-quenching points and four spectral lines; (ii) in the case of applying two RF-driven fields, there are three fluorescence-quenching points and five spectral lines; (iii) when applying three RF-driven fields, there are four fluorescence-quenching points and six spectral lines; and (iv) as expected, when the atomic system coupled by N RF-driven fields, there will be N + 1 fluorescence-quenching points and N + 3 spectral lines. Interestingly enough, the spectral-line enhancement, the spectral-line suppression, and the selective cancellation of fluorescence-quenching can be well controlled just by appropriately modulating the intensities and frequencies of the applied RF fields, respectively. The proposed schemes can be achieved by use of RF-driven fields into hyperfine levels in rubidium atomic systems. These investigations may find applications in high-precision spectroscopy.     

各向异性光子晶体中Λ型原子的自发辐射性质

讨论了各向异性光子晶体中Λ型三能级原子的辐射性质. 研究发现，原子上能级与光子晶体带边的相对位置和两低能级相对位置将直接影响原子的动力学性质及其周围辐射场的性质. 通过数值计算和理论分析，得到了光子晶体中原子周围辐射场在不同位置随时间演化的图像，并讨论了光子晶体对原子辐射谱的影响.     

Energy spectrum of a relativistic two-dimensional hydrogen-like atom in a constant magnetic field of arbitrary strength

We compute, via a variational mixed-base method, the energy spectrum of a two-dimensional relativistic atom in the presence of a constant magnetic field of arbitrary strength. The results are compared to those obtained in the non-relativistic and spinless case. We find that the relativistic spectrum does not present s states.     

Spontaneous emission from a ladder three-level atom in anisotropic photonic crystals

We investigate the spontaneous radiation from a ladder three-level atom embedded in a three-dimensional anisotropic photonic crystal with an external driving field. The properties of the spontaneous emission are dependent strongly on the relative position of the middle level from the band edge. Due to the Autler-Townes splitting by the action of the driving field, the external driving field can also affect the properties of the spontaneous emission. The population exchanged between the upper and the middle levels decreases as the detuning of the external driving field frequency from the corresponding transition frequency increases. The properties of the emission field can be changed or so much as controlled by choosing suitable intensity of the external driving field. The emission spectrum is more complex, and dependent on the location of the observer in this case.     

Hyperfine structure of a hydrogen-like atom due to orbit-orbit,spin-orbit,and spin-spin interactions

A nonrelativistic model of a hydrogen-like atom is considered. This model is used to calculate corrections to the energy spectrum of the atom. The analysis is based on a Hamiltonian that includes the intratomic fields generated by the electron and the nucleus.