Selective Reflection of Potassium Vapor Nanolayers in a Magnetic Field

The selective reflection of laser radiation from the interface between a dielectric window and the atomic vapors confined in a nanocell of thickness L ≈ 350 nm is used to develop effective Doppler-broadening- free spectroscopy of potassium atoms. A small atomic line width and a relation between the signal intensity and the transition probability allowed us to resolve four lines of atomic transitions responsible for the D1 lines of the ³⁹K and ⁴¹K isotopes. Two groups containing four atomic transitions form in an applied magnetic field upon pumping by radiation with circular polarization σ⁺ or σ^–. Different intensities (probabilities) of transitions for the σ⁺ and σ^– excitations are detected in magnetic field B₀ ≈ A _hfs /μ_B ≈ 165 G (A _hfs is the magnetic dipole constant for the ground state and μ_B is the Bohr magneton). A substantially different situation is observed at B ? B₀, since high symmetry appears for the two groups formed by radiation with circular polarization σ⁺ or σ^–. Each group is the mirror image of the other group with respect to the frequency of the 4²S_1/2–4²P_1/2 transition, which additionally proves the occurrence of the complete Paschen–Back regime of the hyperfine structure at B ≈ 2.5 kG. A developed theoretical model well reproduces the experimental results. Possible practical applications are described. The results obtained can also be applied to the D₁ lines of ⁸⁷Rb and ²³Na.     

Faraday effect on the Rb <Emphasis Type="Italic">D</Emphasis> <Subscript>1</Subscript> line in a cell with a thickness of half the wavelength of light

The rotation of the radiation polarization plane in a longitudinal magnetic field (Faraday effect) on the D₁ line in atomic Rb vapor has been studied with the use of a nanocell with the thickness L varying in the range of 100–900 nm. It has been shown that an important parameter is the ratio L/λ, where λ = 795 nm is the wavelength of laser radiation resonant with the D₁ line. The best parameters of the signal of rotation of the radiation polarization plane have been obtained at the thickness L = λ/2 = 397.5 nm. The fabricated nanocell had a large region with such a thickness. The spectral width of the signal reached at the thickness L = 397.5 nm is approximately 30 MHz, which is much smaller than the spectral width (≈ 500 MHz) reached with ordinary cells with a thickness in the range of 1–100 mm. The parameters of the Faraday rotation signal have been studied as functions of the temperature of the nanocell, the laser power, and the magnetic field strength. The signal has been reliably detected at the laser power P_L ≥ 1 μW, magnetic field strength B ≥ 0.5 G, and the temperature of the nanocell T ≥ 100°C. It has been shown that the maximum rotation angle of the polarization plane in the longitudinal magnetic field is reached on the F_g = 3 → F_e = 2 transition of the ⁸⁵Rb atom. The spectral profile of the Faraday rotation signal has a specific shape with a sharp peak, which promotes its applications. In particular, Rb atomic transitions in high magnetic fields about 1000 G are split into a large number of components, which are completely spectrally resolved and allow the study of the behavior of an individual transition.     

Possibility of the use of the magnetic field for creating a quantum filter on the <Emphasis Type="Italic">D</Emphasis><Subscript>1</Subscript><Superscript>87</Superscript>Rb line

The possibility of the use of the F = 2?F = 1 transition of the D ₁ absorption line of the ⁸⁷Rb atom for creating of a single-photon quantum filter based on coherent population trapping (CPT) has been analyzed. It has been shown that the external magnetic field is necessary for ensuring the creation of the quantum filter on boson isotopes of alkali atoms. The field strength should be enough for the manifestation of the splitting of the Zeeman CPT resonances that is much larger than their spectral widths. The splittings of the CPT resonances, which characterize the nonlinearity of the Zeeman effect, have been measured for the ⁸⁷Rb atom and the possibility of the use of this system for the quantum filter is concluded.     

Experimental investigation of the dark pseudoresonance on the <Emphasis Type="Italic">D</Emphasis>1 line of the <Superscript>87</Superscript>Rb atom excited by a linearly polarized field

The measurements of the metrological characteristics (amplitude, width, and shift in the magnetic field) of the dark pseudoresonance, which was proposed by Kazakov et al. [quant-ph/0506167] as the reference resonance for an atomic frequency standard, are reported. It has been shown that the characteristics of the pseudoresonance are worse than those of the unsplit electromagnetically induced transparency resonance for the excitation scheme with the lin‖lin polarization on the D1 line of the ⁸⁷Rb atom.     

Transverse polarization of the lepton in the decay process <Emphasis Type="Italic">B</Emphasis> → <Emphasis Type="Italic">Dlν</Emphasis><Subscript>l</Subscript> due to electromagnetic final-state interaction

The emergence of transverse polarization of the lepton in the decay processes B⁰ → D^?l⁺ν_l and \(B^ + \to \bar D^0 l + \nu _l \) for l = τ, μ is studied on the basis of the Standard Model in the leading approximation of heavy-quark effective theory. It is shown that a nonzero transverse polarization appears owing to electromagnetic final-state interactions at the one-loop level. Diagrams involving D and D* mesons in the intermediate state and making a nonzero contribution to the transverse polarization of the outgoing lepton are considered. If only these mesons are taken into account in evaluating the mean values of the τ-lepton polarization in the decays B⁰→D^?τ⁺ν_τ and \(B^ + \to \bar D^0 \tau ^ + \nu _\tau \), the results are 2.60×10^-3 and ?1.59×10^?3, respectively. The corresponding values of the transverse muon polarization averaged over the Dalitz plot are 2.97×10^?4 and-6.79×10^?4.     

Kontinuierlicher Absorptionsquerschnitt von Argon im Bogenplasma

Optical pumping on Cs¹³³ atoms was performed by means of a new transmission technique. The cesium vapor was pumped towards equilibrium by an intensive circulary polarizedD ₁ orD ₂ light beam. A weakD ₁ detecting beam was polarized alternately σ⁺, σ^? and allowed one to measure continuously amount and sign of the absorption difference between σ⁺ and σ^? light. The measured signals are proportional to the electron spin polarization. The new technique was used to investigate the influence of Cs buffer gas collisions on the pumping cycle and to measure the influence of radio frequency induced Zeeman transitions on the ground state polarization. In addition the variation of magnetic field and of pumping light intensity and polarization was studied. Some measurements demonstrate the high sensitivity of the applied method. The obtained qualitative results are discussed and further experiments are proposed.     

Coherent population trapping resonance on the <Superscript>87</Superscript>Rb D<Subscript>1</Subscript> line in the field of circularly polarized counterpropagating waves

The study of the previously proposed method for improving the parameters of the coherent population trapping resonance on the ⁸⁷Rb D₁ line using two counterpropagating bichromatic fields with orthogonal circular polarizations is continued. The method consists in elimination of trap states existing in the conventional σ⁺ measurement scheme and limiting the resonance amplitude. The resonance parameters are studied in a wide range of pump radiation intensities and in various configurations implementing the σ⁺-σ^? scheme.     

Polarisationseffekte in der Hyperfeinstruktur von65Cu I, 3d 94s 2 m 2 D

The hyperfinestructure of the transition⁶⁵CuI, 3d ¹⁰4p ² P _3/2—3d ⁹4s ² m ² D _5/2 was investigated by optical interferometric methods. For the hfs-factors the following values were found:A(⁶⁵Cu,m ² D _5/2)=26,79(3) mK andB(⁶⁵Cu,m ² D _5/2)=5,81(10) mK. The core polarization of them ² D-terms and the Sternheimer corrections in the calculation of the quadrupolmoment of copper 65 from theB-factors of the terms 3d ⁹ 4s² m ² D and 3d ¹⁰ 4p ² P _3/2. were discussed.     

Dissociative Excitation of the Even Quartet and Sextet Levels of the Manganese Atom by Collisions of Electrons with Manganese Diiodide Molecules

Dissociative excitation of even quartet and sextet levels of the manganese atom by electron collisions with manganese diiodide molecules was studied experimentally. Twelve excitation cross-sections for transitions from quartet levels and 23 cross-sections for transitions from sextet levels were measured at an incident electron energy of 100 eV. The optical excitation function (OEF) was recorded in the range of electron energies 0?100 eV for transitions originating at the 3d⁵4s4de⁶D_J levels. The potential channels of dissociative excitation in the range of low electron energies (E < 22 eV) were discussed.     

Specific features of magneto-optical spectra of Tb<Subscript>3</Subscript>Ga<Subscript>5</Subscript>O<Subscript>12</Subscript>

The spectra of magnetic circular dichroism in the range of the ⁷ F ₆→⁵ D ₄ absorption band and the spectra of magnetic circular polarization of luminescence in the range of the ⁵ D ₄→⁷ F ₅ band in the terbium-gallium garnet Tb₃Ga₅O₁₂ are studied at a temperature of 80 K. The optical transitions between the Stark sublevels of the ⁷ F ₆, ⁷ F ₅, and ⁵ D ₄ multiplets are identified based on the analysis of the magneto-optical and optical spectra. It is shown that the experimentally determined symmetry and energy of the Stark sublevels of these multiplets confirm the results of numerical calculations of the energy spectrum of the Tb³⁺ rare-earth ion in terbium-gallium garnet.     

Selective reflection of laser radiation from submicron layers of Rb and Cs atomic vapors: Applications in atomic spectroscopy

We studied selective reflection (SR) of laser radiation from a window of a nanocell with thickness L ~ λ_1,2/2 filled with Rb and Cs atoms, where λ₁ = 780 nm and λ₂ = 852 nm are the wavelengths resonant with the D₂ laser lines for Rb and Cs, respectively. It is demonstrated that the negative derivative of the SR signal profile for L > λ/2 changes to the positive one for L < λ/2. It is shown that the real-time formation of the SR signal profile derivative (SRD) with the spectral width 30–40 MHz and located at the atomic transition is, in particular, a convenient frequency marker of D₂ transitions in Rb and Cs. The amplitudes of SRD signals are proportional to the atomic transition probabilities. A comparison with the known saturated absorption (SA) method demonstrated a number of advantages, such as the absence of cross-over resonances in the SRD spectrum, the simplicity of realization, a low required power, etc. An SRD frequency marker also operates in the presence of the Ne buffer gas at a pressure of 6 Torr, which allowed us to determine the Ne–Rb collisional broadening, whereas the SA method is already inapplicable at buffer gas pressures above 0.1 Torr. The realization simplicity makes the SRD method a convenient tool for atomic spectroscopy. Our theoretical model well describes the SRD signal.     

Spectral-luminescent properties of Eu<Superscript>3+</Superscript> ions in inorganic D<Subscript>2</Subscript>O and POCl<Subscript>3</Subscript>-SnCl<Subscript>4</Subscript> solvents

Absorption and luminescence spectra of Eu³⁺ ions in D₂O and POCl₃-SnCl₄ inorganic solvents were measured. Oscillator strengths and spontaneous radiation transition probabilities for the most intense electron transitions in Eu³⁺ were calculated. Judd-Ofelt parameters, the radiative lifetime of the ⁵ D ₀ metastable level of Eu³⁺ in D₂O-Eu³⁺ and POCl₃-SnCl₄-Eu³⁺ solutions, and matrix elements for radiative transitions from the ⁵ D ₀ level were determined. The luminescence lifetime of the ⁵ D ₀ level of Eu³⁺ in these solutions was measured. The photoluminescence quantum yield for transitions from the ⁵ D ₀ level of Eu³⁺ in ⁵ D ₀ and POCl₃-SnCl₄-Eu³⁺ solutions was found to be 0.32 and 0.88, respectively.     

Excitons in monoclinic zinc diphosphide: The <Emphasis Type="Italic">A</Emphasis>-exciton series and Fano effect

The A-exciton series in the absorption spectra of β-ZnP₂ monoclinic zinc diphosphide samples is investigated at different directions of the wave vector and different polarization states of radiation. It is shown that the oscillator strengths determined for the observed transitions are adequately described by the relationship F _n ∝n^?3 characteristic of S-type exciton states. The assumption is made that the A-exciton series is associated with the partially allowed dipole transitions to nS states of the orthoexciton with Γ ₂ ^? (x) symmetry at m _s =0. These states are mixed, to a first approximation, with nS states of the Γ ₂ ^? (z) singlet exciton due to the spin-orbit 2 interaction and are split off by the long-range (nonanalytical) part of the exchange interaction. The Fano antiresonances arise in the absorption spectra at resonances of the A-exciton series when the radiation vector E (or the induction vector D) has a component along the crystallographic axis c. These antiresonances are induced by the configurational interaction of discrete exciton states of the A series with the continuum of the exciton-phonon spectrum due to indirect transitions to the 1S band of the singlet exciton with phonon emission.     

37 Years with the light scalar mesons. The learned lessons

Attention is paid to the production mechanisms of light scalars that reveal their nature. We reveal the chiral shielding of the σ(600) meson. We show that the kaon loop mechanism of the ? radiative decays, ratified by experiment, is four-quark transition and points to the four-quark nature of light scalars. We show also that the light scalars are produced in the two photon collisions via four-quark transitions in contrast to the classic P wave tensor qq? mesons that are produced via two-quark transitions γγ → qq?. We study the mechanism of production of the light scalar mesons in the D _s ⁺ → π⁺π^? e ⁺ν decays: D _s ⁺ → ss?e ⁺ν → [σ(600) + f ₀(980)]e ⁺ν → π⁺π^? e ⁺ν, and compare it with the mechanism of production of the light pseudoscalar mesons in the D _s ⁺ → (η/η′)e ⁺ν decays: D _s ⁺ → ss?e ⁺ν → (η/η′)e ⁺ν. As a result we find support to four-quark nature of light scalars. In the end, we outline the future research program.     

Interrelationship between the polarization moments of different parity upon optical pumping of atoms under the magnetic resonance conditions: I. Experiment on the <Superscript>133</Superscript>Cs and <Superscript>4</Superscript>He atoms

In an experiment with an optical pumping of ¹³³Cs atoms in the 6² S _1/2 ground state, the line shape of the D ^2f magnetic resonance signal for the transverse alignment component oscillating at a double frequency f of a radio-frequency (RF) magnetic field is found to strongly depend on the polarization of pumping radiation. On passage from a linearly polarized pumping light to a circularly polarized (CP) light with a sufficiently strong RF field the ordinary three-peak line with the highest central peak transforms into a two-peak line with a minimum at the center, so that the D ^2f signal line resembles the M ^f signal line of a transverse orientation oscillating at the RF field frequency f. This suggests that the orientation (the first-rank polarization moment (PM)) arising upon CP pumping affects the alignment (the second-rank PM); i.e., the PMs of Cs atoms with different parities of their ranks become coupled. No influence of the polarization of a pumping radiation on the line shape of the D ^2f signal is observed in a similar experiment with the ⁴He atoms in the 2³ S ₁ metastable state.     

Influence of transverse magnetic fields and depletion of working levels on the nonlinear resonance Faraday effect

The nonlinear resonance Faraday effect is studied under the condition of coherent population trapping in ⁸⁷Rb vapor at the D₁-line F=2→F′=1 transition. The influence of transverse magnetic fields on the nonlinear optical Faraday rotation is studied. For the transverse fields perpendicular to the electromagnetic-wave polarization, a simple theoretical model is proposed, which is in good agreement with experimental data. The optimal intensity providing the maximum sensitivity is found based on the results obtained. The influence of working-level depletion on the parameters of Faraday rotation in open systems is studied experimentally and theoretically. The system was closed in the experiment by using an additional laser to increase the sensitivity and extend the dynamic range of measured fields. The importance of compensating for the depletion in the presence of spurious magnetic fields is shown; in particular, the sensitivity was enhanced by a factor of 50 in experiments with a buffer gas.     

Investigation of quadratic stark effect on Rb D<Subscript>2</Subscript> atomic line

Experimental study of the influence of an electric field on the atomic hfs levels of D₂ line of Rb atom, transitions 5S _1/2 ? 5P _3/2, has been performed. For this purpose a sapphire cell with internal electrodes used to produce a constant electric field was elaborated. By using the saturation absorption technique the frequency shifts of all 12 atomic D₂ line transitions were recorded. The results are compared with the theory.     

Präzisionsmessung der Hyperfeinstruktur des 52P3/2-Terms und des 62P3/2-Terms von Rb85 und Rb87

To study the modification of the value of the nuclear quadrupole moment obtained without Sternheimer correction from measurements in states with different principal quantum numbers, the hyperfine structure splitting of the 5² P _3/2 and the 6² P _3/2 excited states of Rb I has been investigated with the optical double resonance method. The experiments, in which isotopic enriched samples of Rb⁸⁵ and Rb⁸⁷ were used, have been carried out in the 5² P _3/2 state without a static magnetic field. In the 6² P _3/2 state, a static magnetic field was applied. For the 5² P _3/2 state, the hyperfine structure constants areA(Rb⁸⁵)=25.029(16) Mc/s,B(Rb⁸⁵)=26.032(70) Mc/s,A(Rb⁸⁷)=84.852(30) Mc/s,B(Rb⁸⁷)=12.611(70) Mc/s. The corresponding constants for the 6² P _3/2 state areA(Rb⁸⁵)=8.25(10) Mc/s,B(Rb⁸⁵)=8.16(20) Mc/s,A(Rb⁸⁷)=27.96(35) Mc/s,B(Rb⁸⁷)=3.95(10) Mc/s. The values of the nuclear quadrupole moments, derived from both finestructure states, can be brought into agreement when the Sternheimer core correction is applied. The Landé factor for the 6² P _3/2 state isg _j=1.334(1).     

Manifestation of the Coster-Kronig effect in the near-threshold electron-impact excitation of the Cd<Superscript>+</Superscript> ion

The near-threshold portions of the energy dependences of the effective excitation cross sections of the resonance transition 4d¹⁰5p²P_1/2° → 4d¹⁰5s²S_1/2 and the two-electron forbidden transition 4d⁹5s²²D_5/2 → 4d¹⁰5p²P_3/2° in the spectrum of the Cd⁺ ion were investigated by the spectroscopic method in crossed electron and ion beams. In the region of energy splitting of the ²P° and ²D levels, a significant resonance contribution of the autoionizing states of cadmium (decaying during the Coster-Kronig process) to the effective excitation cross sections of the noted transitions was revealed for the first time. It is found that the resonance contribution manifests itself much more strongly for the forbidden transition in comparison with the more intense resonance transition; i.e., the manifestation of the Coster-Kronig effect in the electron excitation of ions depends strongly on the cross section of the direct process. It is ascertained that, during the Coster-Kronig process, the main contribution to the resonance excitation of both the resonance and the two-electron forbidden spectral transitions is from the low-lying terms of the series of autoionizing states 4d¹⁰5p(²P_3/2°)ns, md and 4d⁹(²D_3/2)5s²ns, md, which are in the splitting region of the ²P_{1/2, 3/2}° and ²D_{5/2, 3/2} levels, rather than from the high-lying atomic autoionizing states of cadmium, which are located near the ionization limits (corresponding to the and ²P_3/2° and ²D_3/2 levels).     

Collisional Broadening of CO<Subscript>2</Subscript> Transition Lines 10<Superscript>0</Superscript>0–00<Superscript>0</Superscript>1 by Inert Gas Atoms at 300–700 K

The spectrum of excitation of Rydberg states of thallium atoms has been investigated using a collimated atomic beam in a two-step isotope selective laser scheme 6²P_1/2 → 6²D_3/2 → Tl** in the presence of an electric field with a strength of up to 1.5 kV/cm near the level 16F_5/2. The optical transitions 6D_3/2 → 18D_3/2 and 6D_3/2 → 16G_7/2, which were induced by an external electric field and dipole-forbidden, have been studied experimentally. The values for the scalar polarizabilities (in units сm^–1/(kV/сm)²) α₀(16F_5/2) = 3.71 ± 0.3, α₀(18D_3/2) = 11.70 ± 0.25, and α₀(16G_7/2) = 44.1 ± 0.9, which are compared with the calculated one, have been obtained. The new values of energy parameters for the states 18D_3/2 and 16G_7/2 have been determined.