Explanation for the effect of natural strong narrowing of Mössbauer lines on long-lived isomers. Variety of nuclei and media with this effect

The effect of natural strong narrowing (NSN) of Mössbauer lines on long-lived isomers has been explained. This effect was doubted for more than thirty years because its mechanism was unknown. The mechanism of NSN has been revealed. Its threshold condition has been established. The theory of inhomogeneous broad-ening of a line in the case of NSN has been developed. Broadenings owing to magnetic, quadrupole, and 2 ^L -pole hyperfine interactions are suppressed almost to zero at NSN. The mechanism of NSN provides a width about the natural width. The linewidth at NSN is independent of the magnitude and direction of the magnetic field if it is lower than ～100 G. The variety of nuclei and media with NSN or with the collapse of the hyperfine interaction (responsible for NSN) is outlined.     

Experimental test of the theory of effect of natural strong narrowing of Mössbauer lines and a more general effect of collapse of the hyperfine structure because of fluctuations of the Fermi contact field. Role of virtual transitions in these effects

To test the theory of the effect of natural strong narrowing (NSN) of Mössbauer lines on long-lived isomers and a more general effect of collapse of the hyperfine structure (CHFS) because of fluctuations of the Fermi contact field (S.V. Karyagin, JETP Lett. 98, 174 (2013)) with the use of the data obtained by the team led by Davydov (Yu.D. Bayukov et al., JETP Lett. 90, 499 (2009)), the yield of 88.034-keV gamma-ray photons from a silver plate with the ^109m Ag isomer has been analyzed in two variants: (i) the hyperfine structure is resolved and the yield depends on the angle ψ between the wave vector of the photon and the external field H _ex, and (ii) the yield is independent of ψ because of CHFS. It has been shown that variant (ii) better reproduces the experimental data: experimental average count numbers at ψ = 0 and ～π/2 differ from each other only in systematic error the same at 4.2 and 295 K and, moreover, the count numbers with the exclusion of resonance should be independent of ψ; this condition is strongly violated in variant (i) and is well satisfied in variant (ii). The threshold condition of the CHFS for the Fermi field has been obtained with allowance for virtual transitions. The collapse of the hyperfine structure is possible at any lifetimes of nuclear levels at any transitions not only in the gamma range but also in other radiation ranges. It results in the complete depolarization of nuclei and radiation. To estimate the Fermi field from experiments, the field |H _ex| ～ 10⁴ G is necessary.     

Strong natural suppression of the monopole broadening of Mössbauer lines

The study of natural strong narrowing of Mössbauer lines on long-lived isomers is continued. This phenomenon was first correctly detected in [Yu. D. Bayukov, A. V. Davydov, Yu. N. Isaev, G. R. Kartashov, M. M. Korotkov, and V. V. Migachev, JETP Lett. 90, 499 (2009)] and was consistently explained in [S. V. Karyagin, JETP Lett. 98, 174 (2013); 98, 695 (2013)]. Thus, natural strong narrowing is a new effect in spite of its 36-yr prehistory. Since natural strong narrowing is based on the collapse of the hyperfine structure owing to chaos in motion of the nuclear spin, “criteria of chaos” have been introduced for the exchange and virtual collapse mechanisms. Types of nuclei and media with these mechanisms have been indicated. It has been found that the lifetime τ of isomers appropriate for natural strong narrowing is limited by diffusion. The strong natural suppression (below 1/τ ~ 10^–2 s^–1) of monopole (isomer, chemical) broadening has been revealed and explained.     

Experimental observation of the linewidth narrowing of electromagnetically induced transparency resonance

Many theoretical and experimental works show that the effect of electromagnetically induced transparency (EIT) is becoming an important tool for implementation of quantum information science. Nevertheless, EIT is a fragile quantum interference effect; the ideal trans- parency is achieved at exactly the two-photon resonance condition, i.e., when the frequency detuning of two pho- tons is zero. If the frequency detuning of two photons is slightly nonzero, the interference is destroyed and the …     

Cavity induced shift and narrowing of the positronium Lyman-α transition

We report experiments in which the line shape of the Lyman-alpha (1S-2P) transition was measured for positronium (Ps) atoms both inside and outside a porous silica target. The energy interval ΔE for confined atoms was observed to be larger than that of free Ps by 1.26±0.06 meV. A configuration interaction calculation yields results that are consistent with our ～5 nm sample, and suggests that ΔE decreases dramatically for larger cavity diameters. The linewidth of the transition, (0.066±0.004) nm (FWHM), is about half of what one would expect for free Ps at room temperature due to the Dicke line narrowing effect of confinement. Such measurements can be used to determine void sizes in porous films and Ps dynamics therein, and elimination of the Doppler spread of atoms in a porous film could be useful for the efficient excitation of a Ps gas.     

The “strong Kadison inequality” of Woronowicz

In the terminology of [4] it is shown that a normalized positive map ? from a C¹-algebra $\text{A}$ into M₂ is a sum ?=ψ₁+ψ₂, where ψ₁ is completely positive and ψ₂ is completely copositive, if and only if for all a?1 in $\text{A}$ the normalized positive map

$\text{?}{}_{\mathrm{a}}\text{=?(a}{}^2\text{)}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{?(a·a)?(a}{}^2\text{)}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$

satisfies the “strong Kadison inequality” of S.L. Woronowicz ([4]). p. 178).     

Effect of strong interaction inpdμ-mesic molecules

It is shown that the inclusion of the exchange interaction between nuclei of a mesic molecule removes the degeneracy of the Coulomb levels and doubles the levels. For the ground state of thepd-molecular ion the splitting is estimated to amount to E10^–2 eV. Possible experiments for detection of this effect are discussed.     

Ionization energies of beryllium in strong magnetic fields

We have develop an effective frozen core approximation to calculate energy levels and ionization enegies of the beryllium atom in magnetic field strengths up to 2.35×105T. Systematic improvement over the Hartree-Fock results for the beryllium low-lying states has been accomplished.     

Ultrathin atomic vapor film transmission spectroscopy: analysis of Dicke narrowing structure

Transmission sub-Doppler spectroscopy with confined atomic vapor film between two dielectric walls is theoretically studied. Because of atoms flying from wall to wall, where they get de-excited, the atom-field interaction time is anisotropic so that the contribution of slow atoms is enhanced, a sub-Doppler transmission spectroscopy (Dicke narrowing effect) can be obtained when the thickness of the film is much small or comparable with the wavelength even at small angle oblique incidence. It is feasible to get a sub-Doppler structure in a new region (L < λ/4) in experiments.     

Mössbauer study of natural wolframites

Natural Wolframite, (Fe _x Mn_1?x )WO₄ withx=0.95 to 0.41, obtained from seven different sites of two quartz-wolframites deposits of Degana and Sirohi in Rajasthan. India, have been studied by Mössbauer spectroscopy down to 20 K. X-ray diffraction studies with a monochromatic Cu radiation (λK_a-1.5405 Å), were carried out to determine the value ofx. The Mössbauer spectra of all seven samples were recored at 300, 200, 100, 50, 40, 30 and 20 K, and were least square fitted for different sites. The Mössbauer parameters are attributed to a high spin ferrous ion in a quite distorted octahedral symmetry, and only one sextet has been resolved below transition temperature.     

Recurrence spectra of Li atom in strong external fields

Based upon our previous work [Commun. Theor. Phys.. 40,702 (2003)], we developed the closed orbit theory from two degrees of freedom to three non-separable degrees of freedom and calculated the recurrence spectra of Li Rydberg atom in strong perpendicular electric and magnetic fields. The Fourier transformed spectra of Li atom has allowed direct comparison between the resonance peaks and the scaled action values of closed orbits, whereas the nonhydrogenic resonance can be explained in terms of the new orbits created by the core scattering. The semiclassical result is in good agreement with the quantum one, which suggests that our calculation is correct.     

Anomalies of the natural convection of water near 3.98°C

Natural convection of water in a cylindrical cavity with an open surface at a temperature of about 3.98°C (temperature of the maximum water density) is accompanied by typical anomalies on time dependences of temperatures of water layers. In particular, stabilization of temperature T_st is observed in the bottom region of the cavity and duration of such stabilization t_st may reach several hours depending on the experimental conditions. The results for solutions of sodium chloride and ethanol at a relatively low rate of water cooling show that temperature T_st coincides with temperature T_max corresponding to the maximum density of solutions.     

Superlattices consisting of “lines” of adsorbed hydrogen atom pairs on graphene

The structures and electron properties of new superlattices formed on graphene by adsorbed hydrogen molecules are theoretically described. It has been shown that superlattices of the (n, 0) zigzag type with linearly arranged pairs of H atoms have band structures similar to the spectra of (n, 0) carbon nanotubes. At the same time, superlattices of the (n, n) type with a “staircase” of adsorbed pairs of H atoms are substantially metallic with a high density of electronic states at the Fermi level and this property distinguishes their spectra from the spectra of the corresponding (n, n) nanotubes. The features of the spectra have the Van Hove form, which is characteristic of each individual superlattice. The possibility of using such planar structures with nanometer thickness is discussed.     

Analysis of the influence shifts of the acetylene of various effects on frequency saturated absorption lines

Frequency shifts of the acetylene saturated absorption lines at 1.5μm with temperature, gas pressure and laser power have been investigated in detail. The second-order Doppler effect, the recoil effect, the Zeeman effect, the pressure shift and the power shift are taken into consideration. The magnitudes of those shifts caused by various effects are evaluated. In order to reproduce the stability of 5.7 × 10^-14 obtained by Edwards, all necessary conditions are given. The results show that when there is a larger external magnetic field, the Zeeman shift could not be neglected, so that the shield should be employed. And the design of a long cavity is advantageous to reduce the influence of the second-order Doppler effect. The results also show that at least 4-2.5℃ temperature control for cavity can effectively prevent several effects and improve the frequency stability.     

Numerical study of laser-induced collision process in Eu-Sr in strong field

Theoretically based on the four-level model, one LICET process in Eu-Sr system in both weak and strong fields was calculated by immediate numerical integrations. Numerical results in weak field are in fair to good agreement with analytical ones. Numerical results in strong field show that: (a) the peak of the LICET profiles moves to the violet side and the tuning range of the profiles obviously becomes narrower when the laser field intensity increases; and (b) numerical results in strong field differ a lot from analytical ones, which indicates that in strong field, the analytical expressions are not applicable any longer.     

Collisional parameters of N2 broadened methane lines in the R9 multiplet of the 2ν3 band. Multispectrum fittings of the overlapping spectral lines

A high-sensitive two-channel photo-acoustic (PA) spectrometer with a near infrared diode laser was used to make precise measurements of N₂-broadened methane spectra in the R9 multiplet of 2ν₃ band. For the accurate retrieval of spectroscopic line parameters (intensities, positions at zero pressure, pressure-shifting and -broadening, collisional narrowing and line mixing coefficients) from the methane PA spectra, a program based on a multispectrum fitting procedure has been used. The multispectrum least squares fitting procedure is based on a relatively simple line profile model and on the linear pressure dependences of the line profile parameters. The line parameters were determined for 11 lines of the methane 2ν₃ R9 multiplet. The results have been compared with other available data.     

Influence of strong magnetic field on β decay in the crusts of neutron stars

βdecay in the strong magnetic field of the crusts of neutron stars is analysed by an improved method. The reactions ⁶⁷ Ni(β^-)⁶⁷ Cu and ⁶² Mn\beta ^-62 Fe are investigated as examples. The results show that a weak magnetic field has little effect on βdecay but a strong magnetic field (B>10¹²G) increases β decay rates obviously. The conclusion derived may be crucial to the research of late evolution of neutron stars and nucleosynthesis in r-process.     

Topological aspect of vortex lines in two-dimensional Gross—Pitaevskii theory

Using the -mapping topological theory, we study the topological structure of vortex lines in a two-dimensional generalized Gross-Pitaevskii theory in (3+1)-dimensional space-time. We obtain the reduced dynamic equation in the framework of the two-dimensional Gross-Pitaevskii theory, from which a conserved dynamic quantity is derived on the stable vortex lines. Such equations can also be used to discuss Bose-Einstein condensates in heterogeneous and highly nonlinear systems. We obtain an exact dynamic equation with a topological term, which is ignored in traditional hydrodynamic equations. The explicit expression of vorticity as a function of the order parameter is derived, where the δ function indicates that the vortices can only be generated from the zero points of Φ and are quantized in terms of the Hopf indices and Brouwer degrees. The -mapping topological current theory also provides a reasonable way to study the bifurcation theory of vortex lines in the two-dimensional Gross-Pitaevskii theory.