Quenching of SO2 phosphorescence by a magnetic field

Phosphorescence excitation spectra of the ã³B₁← [Xtilde]¹A₁ transition of SO₂ were measured in the absence and presence of a magnetic field (B = 0?44 T², P(SO₂) = 0?7 Torr). The absorption and phosphorescence excitation spectra of the ã³B₁← [Xtilde]¹A₁ transition of SO₂ measured in the absence of a magnetic field show that the relative intensity of the bands of the phosphorescence excitation spectrum is smaller than the relative intensity of the corresponding bands of the absorption spectrum beginning with the (0, 2, 0) band. In the presence of a magnetic field, the intensity of the phosphorescence excitation band falls, for ν_exc> 26400 cm^-1. Under the direct excitation of the ã³B₁← [Xtilde]¹A₁ transition, the dependence of the magnetic quenching of the SO₂ phosphorescence on the excitation frequency (ν_exc) was studied at P(SO₂) = 0?7 Torr and B = 0?44 T. The dependence of the magnetic field effect on ν_excshows that only the vibrationally excited levels of the ã³B₁ state are sensitive to an external magnetic field. The magnetic field strength and the pressure dependence of the magnetic field effects were studied under indirect excitation of the ã³B₁← [Xtilde]¹A₁ transition at λ_exc = 308 nm. The magnetic field and the pressure dependence were investigated for pure SO₂ and for SO₂ + RH (RH n-C₅H₁₂) mixtures. It was found that the magnetic field effect was saturated at B ? 0?25 T. The saturation value (Gr = l(0?3 T)/l(0)) increases with increasing gas pressure. The magnetic field, the pressure and the excess vibrational energy (ν_excess) dependence of the magnetic quenching of SO2 phosphorescence show that the data observed can be explained by an indirect mechanism within the framework of a low level density approximation.     

Hydrogen-like atom in a superstrong magnetic field: Photon emission and relativistic energy level shift

Following our previous work, additional arguments are presented that in superstrong magnetic fields B ? (Zα)² B ₀, B ₀ = m ² c ³/e? ≈ 4.41 × 10¹³ G, the Dirac equation and the Schrödinger equation for an electron in the nucleus field following from it become spatially one-dimensional with the only z coordinate along the magnetic field, “Dirac” spinors become two-component, while the 2 × 2 matrices operate in the {0; 3} subspace. Based on the obtained solution of the Dirac equation and the known solution of the “onedimensional” Schrödinger equation by ordinary QED methods extrapolated to the {0; 3} subspace, the probability of photon emission by a “one-dimensional” hydrogen-like atom is calculated, which, for example, for the Lyman-alpha line differs almost twice from the probability in the “three-dimensional” case. Similarly, despite the coincidence of nonrelativistic energy levels, the calculated relativistic corrections of the order of (Zα)⁴ substantially differ from corrections in the absence of a magnetic field. A conclusion is made that, by analyzing the hydrogen emission spectrum and emission spectra at all, we can judge in principle about the presence or absence of superstrong magnetic fields in the vicinity of magnetars (neutron stars and probably brown dwarfs). Possible prospects of applying the proposed method for calculations of multielectron atoms are pointed out and the possibility of a more reliable determination of the presence of superstrong magnetic fields in magnetars by this method is considered.     

Study of the hybrid state of Y9Co7(2.0≲T≲ 6 K) by means of zero field muon spin relaxation

Muon spin relaxation functions were measured in the magnetic superconductor Y₉Co₇ for T ? 2.0 K and at zero applied field. In the paramagnetic region (T ? 6.0 K) the depolarization of the muon spins is due to the quasi-static ⁵⁹Co nuclear moments. The onset of the magnetic state results in a fast-relaxing signal that corresponds to dipolar fields of the order of 100 0e; this component grows steadily in amplitude as the material transists from the hybrid into the superconducting state. The data are consistent with the high degree of inhomogeneity of the (not long-range) ordering and coexisting but non-competing magnetic and superconducting properties in the “hybrid” state (2<T<5K).     

Anisotropy of the mixed-state resistance of Tl2Ba2CaCu2O8 single crystals

The electrical resistance of single crystals of the high-temperature superconductor Tl₂Ba₂CaCu₂O₈ has been measured as a function of the angle θ between the direction of the magnetic field and the current-carrying CuO₂-planes. The resistance is maximal for θ = 90° ( B ?CuO₂-planes) and decreases to a minimum at θ = 0°. For small angles an anomalous enhancement of the resistance is found. While the general shape of the resistance is generated by the motion of “pancake vortices” in the CuO₂-planes, the anomaly is due to “Josephson vortices” moving perpendicular to the planes.     

Transport properties of conduction electrons in n-type inversion layers in (100) surfaces of silicon

The conductivities of n-type inversion layers in (100) surfaces of p-type silicon were measured extensively as functions of electron density in the inversion layer, the ambient temperature and the applied magnetic field. Measurements were made on the carefully fabricated four “classes” of MOS field-effect transistors whose maximum mobilities at 4·2K were 14,000, 8000, 6800 and 1500 cm²/V·sec, respectively. From the temperature dependence of the mobility, dominant momentum scattering was reasonably ascribed to surfon at 100 ～ 300 K. and degenerate or non-degenerate coulomb scattering at lower temperatures as treated by Stern and Howard. From the curves of conductivity vs temperature at low temperatures and low electron concentration for specimens with high mobilities, an activation energy of 1·2 meV, relating to the shallow bound states associated with the lowest electrin sub-band, was observed. The conductivity σ_xx of the inversion layer in a strong transverse magnetic field showed behaviors like those of completely free electrons without effects belonging to its material in its oscillation pattern. That is, the peak value of σ_xx as a function of the gate voltage V_R dependend only on the Landau index. The σ_xx as a function of the magnetic field H at a constant V_R showed a similar Shubnikov-de Haas (SdH) type oscillation to that of three dimensional one. The SdH oscillation gave an “apparent” g-value g* which ranges from 2 to 5 depending on the surface carrier density n_s, due to the change in the ratios of the widths of the Landau levels to the level separation. The “reasonable” g-value of the conduction electrons in the inversion layer has been determined using a modified tilted magnetic field method. The g-value at the fixed magnetic field was independent of surface carrier density n_s and tended to 2 in the extreme strong magnetic field.Discussion is made of the g-value relating to the Landau level width and the energy gaps in the density of states under strong magnetic field.     

Single crystal magnetic susceptibility of the quasi-one-dimensional organic conductor (fluoranthene) 2PF6

Magnetic susceptibility was measured on a bundle of single crystals of difluoranthene phosphor hexafluoride [(FA)₂^·+PF₆^?] with external field parallel or perpendicular to the molecular stacking direction. Except for lowest temperatures, where the paramagnetic contribution of sample defects is of importance, magnetic susceptibility is dominated by the strongly anisotropic molecular diamagnetism. Spin paramagnetism is separated in the metallic and semiconducting phase and compared with magnetic resonance results and predictions of available models.     

The magnetic susceptibility of TMTSF-DMTCNQ under pressure

The susceptibility of TMTSF-DMTCNQ was measured in the newly discovered highly-conducting state under pressure. At a pressure of 12 kbar, the susceptibility χ_m (with the core diamagnetism subtracted) changes sign from the room-temperature paramagnetic value and becomes diamagnetic at a temperature of approximately 30 K. At a temperature of 5–10 K χ_m reaches a value of approximately ?7 × 10^?4 emu mole^?1. This value is about 3 times larger than the previously reported diamagnetism of HMTSF-TCNQ.     

Magnetic field effect on the H2CS fluorescence from the first excited singlet state Ã1A2

Fluorescence intensity in thioformaldehide vapours (H₂CS), excited to the ÃA₂ different vibronic levels of the ùA₂ ? [Xtilde]¹A₁ transition, were measured as a function of an external magnetic field. On excitation to these levels, dynamics in zero and non-zero field may be described in the small-molecule limit, with fluorescence exhibiting an almost exponential decay. A magnetic field changes the integrated intensity and decay lifetime of the thioformal-dehide fluorescence induced from different vibronic levels of the ù A₂ state. We found that the magnetic field effect grows at lower gas pressures. The measured field dependences of the magnetic field effect can be fitted using field-saturated functions. The measured data were explained by the indirect mechanism theory (nuclear-spin and electron-spin decoupling mechnism).     

Magnetic moment of pressure quenched cadmium sulfide

Magnetic moment measurements of CdS polycrystalline samples, pressure quenched from above the semiconducting to conducting transition pressure (40 kbars) at rates approaching 10⁶ bars/sec, have been made in a vibrating sample magneto-meter to fields approaching 1000 Oersted. The samples exhibit the complex magnetic behavior of low field diamagnetism (χ > - 5 × 10^-5cgsunits) transforming at fields of several hundred Oersted to positive magnetism (χ > + 3 × 10^-4cgsunits). This magnetic behavior contrasts with unquenched samples which yield the normal diamagnetism of CdS (χ = - 1.5 × 10^-6cgsunits). These anomalous magnetic effects are observed at both room temperatures and LN₂ temperatures at atmospheric pressure.     

Magnetic properties of iron marcasite FeS2

The magnetic susceptibility, χ, of a natural single crystal of marcasite, FeS₂, has been measured between 300K down to 4K. At room temperature χ=0.3×10^?5 emu/g and it is temperature independent down to 10K. Below 10K it increases up to 1.3×10^?5 emu/g. It is concluded that iron in marcasite is in the Fe²⁺ low spin state, and that the 6d electrons occupy the t_2g ground state. Consequently iron in marcasite (FeS₂) is not magnetic in agreement with our Mössbauer spectra recorded at 4.2K in an external magnetic field up to 39.9 kOe. The small value of χ is explained in terms of contributions from ppm impurities. i.e., diamagnetism and Van Vleck paramagnetism.     

Magnetic ordering of Fe atoms in icosahedral Al70−x BxPd30−y Fey quasicrystals

Novel icosahedral quasicrystals, in which Fe atoms possess a magnetic moment, have been found in Al_70?x B_xPd_30?y Fe_y compounds with 5<x<10 and 10<y<20. The compounds have ferromagnetic properties, and their Curie temperature ranges between 280 and 340 K, the saturation magnetization σ _s(5 K)≈7.5 emu/g. It follows from Mössbauer spectra that only a fraction of Fe atoms (12 to 15%) are magnetically ordered at 4.2 K, and the mean saturation field 〈H _hf〉=96 kOe. The isomer shift values confirm that the atomic volume of magnetic Fe sites is larger than that of nonmagnetic Fe sites. The magnetic properties of these quasicrystals can be interpreted in terms of large magnetic clusters with a size of 185 to 290 Å. This size correspond to about 4×10⁴ “unit cells,” hence the magnetic state can be described in terms of bulk parameters. The localized magnetic moment of Fe atoms is tentatively ascribed to bonding between Fe and B, similarly to that in the amorphous Fe_～50B_～50 alloy.     

Some anomalies in the Ne(I)(744/736 Å) photoelectron spectra of N2O

The Ne(I) 774/736 Å photoelectron spectra of N₂O are reported for the X?²Π state of N₂O⁺. The spectra in general do not show any autoionization behavior to the extent reported for CO₂ and CS₂. There is an apparent “enhancement” of the 101 level by the 744 Å line. In contrast to the He(I) 584 Å PES, the intensity ratio for the 100 and 001 levels are reversed when excited by Ne(I) 736 Å radiation.The spectra also show excitation to higher vibrational levels of N₂O⁺X²Π. This can be explained within the framework of autoionization of a Rydberg state whose core is similar to that of the B? state of N₂O⁺.     

On the Energy of a “One-Dimensional” Two-Electron Atom

Based on the perturbation theory and variational method long known for a “three-dimensional” atom, the ground and first excited state energies are calculated for a “one-dimensional” two-electron atom in the “one-dimensional ortho-helium” configuration, which can be obtained experimentally in principle, as has been already done for a Na Bose condensate, or produced in a super strong magnetic field B ? (2α)²B₀ (B₀ = m²c³/e? ≈ 4.41 × 10¹³ G). The “screening constant” σ for this atom in the ground and excited states was about 0.20 and 0.17, 0.18, respectively, depending on the relative parity PP' of the electronic states, which is somewhat smaller than in “two-dimensional” and “three-dimensional” variants (in these cases, this constant in the ground state is almost the same and about 0.3). The frequencies of the main spectral lines of a “onedimensional” He atom representing a doublet split over the relative parity PP' are found. The presence of the close lines of this doublet in the emission spectrum of magnetars at frequencies ω_{1, 2} ≈ {1.15; 1.17}α²(c/λC) (α = e²/?c, λ_C =?/mc) corresponding to the “one-dimensional ortho-helium” would suggest the existence of a superstrong magnetic field in such astrophysical objects.     

High field magnetic susceptibility of individual single crystals of the organic conductor (fluoranthene)2PF6

Using single crystals of a sufficient size (4–7 mg) and a high quality (about 5 × 10^-4 paramagnetic defects per formula unit) we measured the anisotropic static magnetic properties of the quasi-1d organic conductor (FA)₂PF₆ in external fields of up to 70 kOe. Thus the strong anisotropy of the molecular diamagnetism was determined for the first time. The contribution of the conduction electrons to the static susceptibility of (FA)₂PF₆ was separated. We analysed the influence of fluctuations (pseudogaps) in the metallic high temperature phase and we derived the temperature dependence of the energy gap in the low-temperature (T < 185 K) semiconducting phase of (FA)₂PF₆.     

Magnetic susceptibility of iron pyrite (FeS2) between 4.2 and 620 K

The magnetic susceptibilities (χ) of several natural single crystals of iron pyrite (FeS₂) have been measured between 4.2 and 620 K with a force magnetometer. The measured susceptibilities are shown to related to the magnetic impurities present in the samples. For a pure sample, χ = 1.7 × 10^?7 emu/g at room temperature, with a small monotonic increase of χ with temperature. The results for a pure sample are interpreted in terms of contributions from diamagnetism and Van Vleck paramagnetism.     

Magnetic field dependence of the thermoelectric power of n - type gallium arsenide in the extreme quantum limit

The effect of the quantization of the electron energy levels in a strong transverse magnetic field H on the low-temperature thermoelectric power (TEP) S of a high-purity isotropic semiconductor ($\text{n}$ - type gallium arsenide GaAs) is investigated theoretically. The “electron-diffusion” (S_e) and “phonon-drag” (S_p) components of S( = S_e + S_p) are calculated in the extreme quantum limit, when all the electrons in the conduction band are concentrated in the lowest Landau level. The transition to nondegeneracy, which takes place when the bottom of the lowest Landau level is driven through the Fermi level, has a large effect on the variations of S_e and S_p with magnetic field. The results are illustrated with numerical calculations for $\text{n}$ - type GaAs at 4.2 K with 1.2 × 10¹⁶ cm^-3 electrons.     

NQR study of spin-freezing in superconducting La2−x Sr x CuO4: the example ofx = 0.06

Nuclear quadrupole resonance (NQR)¹³⁹La and⁶³Cu spin-lattice relaxation rateT ₁ ^t-1 measurements in a La_1.94Sr_0.06CuO₄ single crystal are described. Slowing-down of Cu²⁺ spin fluctuations is evidenced through a dramatic increase of¹³⁹ T ₁ ^?1 on cooling. While the onset of diamagnetism occurs atT _c = 8 K,¹³⁹ T ₁ ^?1 has a peak atT _g ? 5 K, when the characteristic frequency of magnetic fluctuations reaches the NQR frequencyv _Q ? 9 MHz. In agreement with a number of previous studies, these results show that the so-called “cluster spin-glass” phase persists in the superconducting regime. Issues concerning the coexistence of the two phases are discussed.     

Two schemes ofη−η′-mixing

Proceeding from the expansion of composite operators in interpolating hadronic fields, the width of the decays η(η′)→γγ andJ/ψ→η(η′)γ have been calculated. Two mechanisms of pseudoscalar field mixing (“mass-mixing” and “current-mixing”) are considered. In the given schemes, the values of η?η′-mixing angle θ _p are, respectively, (?15.0±1.8)^o and (?19.7±2.2)^o.     

Hyperfine interactions in Sc<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Y<Subscript>x</Subscript>Fe<Subscript>2</Subscript> cubic Laves alloys

Effects of hybridization of 3d bands of iron with 3d bands of scandium and 4d bands of yttrium in Sc_1?xY_xFe₂ cubic Laves alloys (0≤_x≤1) are studied by the nuclear magnetic resonance method. The concentration dependences of the lattice parameters a, saturation magnetization σ, and hyperfine fields at the ⁵⁷Fe, ⁴⁵Sc, and ⁸⁹Y nuclei—as well as the ²⁷Al impurity nuclei, whose atoms substitute iron atoms in the lattices of these alloys—are measured. The “local” and “induced” contributions to hyperfine fields at the ⁵⁷Fe nuclei are separated and the magnetic moments at iron atoms are estimated. It is found that the hybridization effect leads to the formation of magnetic moments at Sc and Y atoms (whose direction is opposite to the direction of the magnetic moment at iron atoms) and is responsible for the ferrimagnetic structure in Sc_1?xY_xFe₂ alloys.     

Anomalous acid proton self-diffusion in N(CH3)4HSO4 — A candidate for proton superionic conductivity

The appearance of a “liquid-like” proton T₂ component above 100°C and the relatively high value of the proton self-diffusion coefficient D = (5–8) × 10^-7cm²sec^-1 between 175°C and 200°C demonstrate the onset of a super-ionic state in N(CH₃)₄HSO₄. The ratio between the “liquid” and “solid” like components shows that acid protons are responsible for the high ionic conductivity.