This mysterious liquid 3He

The spin contribution to the heat capacity and entropy of ³He has been singled out. With increasing T the spin entropy reaches a constant value, different from ln 2. The spin contribution ≈ ln T can be observed in the temperature dependence of the pressure.     

Non standard weak bosons at HERA collider

We compare the effects of non-standard weak bosons (NSB) expected fromE ₆-superstrings (Z′), strong Higgs (V ₀) and composite (spin 0, 1, 2) models by using the classical inclusive deep-inelastic “ep” scattering at HERA energies. TheX ² associated to polarized and unpolarized cross-sections, as well as the six combinations of asymmetries, allow us to derive significant bounds on the masses of the new bosons of various spins associated to some composite models with exception of the excitedZ ^*. We have also obtained some lower bounds for spin one bosons of different models (Z′,V ₀,Z ^*) which are stronger than the present experimental limits.     

Lifetimes of a dipole cascade in192Hg

Lifetimes of ten states with spins between 23 and 32 have been measured in a cascade of dipole transitions in¹⁹²Hg using the Doppler-shift recoil-distance method. Average reduced transition probabilities, deduced from the lifetimes, are B(M1)≈0.01 and 1.1µ _n ² in the lower and higher spin region of the cascade, respectively, and B(E2)≈0.13 (eb)². The jump in the B(M1) values can be explained by different multi-quasiparticle configurations in the lower and higher spin regions of the band.     

Mössbauer spectroscopic studies of spin crossover in tris(N, N′-dialkyldithiocarbamato) iron (III) complexes: effect of alkyl substituents

Spin crossover behavior in tris(N,N′-dialkyldithiocarbamato) iron(III) complexes with varying alkyl groups has been studied by variable temperature magnetic moment and Mössbauer spectral studies. All the complexes may be divided into three broad groups; high spin (μ _eff > 4.8 BM), intermediate spin (μ _eff?=?3.5???4.6 BM) and low spin (μ _eff?< 3.2 B.M). Room temperature (RT) Mössbauer spectra exhibit an asymmetric doublet resolved into two doublets corresponding to high and low spin states. Estimated % contributions of HS and LS states and calculated μ _eff were comparable with the experimentally determined values. It has been shown that some complexes undergo spin crossover, ⁶A₁g→²T₂g whereas others exhibit spin transitions ⁶A₁g →⁴T₁g or ⁴T₁g → ²T₂g. IR spectra show characteristic ν _(Fe???S) bands in the region 208–285 (HS) and 311–380 cm^???1 (LS). Nature of alkyl groups affects the spin state.     

Lattice dynamical behaviour of Fe(II) spin crossover compounds from57Fe Mössbauer spectroscopy

Temperature-dependent transmission Mössbauer spectroscopy was used to determine the Debye-Waller factors and hyperfine interaction parameters of the Fe(II) spin crossover complexes: Fe(phen)₂(NCS)₂, Fe(bipy)₂(NCS)₂ and Fe(py)₂phen(NCS)₂, and also the non-crossover system Fe(py)₄(NCS)₂. In the spin conversion systems, thef _LS is higher than thef _HS, which indicates different lattice dynamical properties at the metal sites in the¹A₁ and⁵T₂ configurations, and is discussed in relation to the metal-ligand bonding interactions in the two spin states.     

Spin Echo Spectrometry Using Very Cold Neutrons

Concept of spin echo spectrometer on very cold neutrons (wavelengths λ ~ 10?30 nm) to provide extra high resolution in energy transfer (ΔE ~ 10^–13 eV) has been proposed. Simultaneous measurements of spin echo signals at different wavelengths will be realized using broadband spin flippers in combination with Fourier-analysis of λ-spectrum. The application of very cold neutrons should extend the spin echo time diapason radically, t ~ 10^–12?10^–3 s. This promises to open a set of novel scientific areas including the spectroscopy of chemical reactions and catalytic processes, conformational transitions in polymers and biological molecules, dynamic modes in carbon structures (fullerenes, nanotubes, graphenes) at scales from few nanometers to microns. Presently, the development of NSE-spectrometer on VCN becomes relevant since the project of ultra cold neutron source at WWR-M reactor (PNPI) is in progress.     

Exponential depletion of neutral dangling bonds density (D) by rare-earth doping in amorphous Si films

In this work we study the effect reduction in the density of dangling bond species D⁰ states in rare-earth (RE) doped a-Si films as a function concentration for different RE-specimens. The films a-Si_1−xRE_x, RE=Y³⁺, Gd³⁺, Er³⁺, Lu³⁺) were prepared by co-sputtering and investigated by electron spin resonance (ESR) and Raman scattering experiments. According to our data the RE-doping reduces the ESR signal intensity of the D⁰ states with an exponential dependence on the rare-concentration. Furthermore, the reduction produced by the magnetic rare-earths Gd³⁺ and Er³⁺ is remarkably greater than that caused by Y³⁺ and Lu³⁺, which led us to suggest an exchange-like coupling between the spin of the magnetic REs³⁺ and the spin of silicon neutral dangling bonds.     

Fragmentation of the yrast band in186Os atI π =18+ and disappearance of the collective minimum

High-spin states in¹⁸⁶Os have been populated by the¹⁸⁶W(⁴He,4n)-reaction at 55MeV. The emittedγ-radiation was detected with the OSIRIS spectrometer. The yrast band, for which the nucleus has a prolate shape, was found to terminate atI ^π =18⁺. Theγ-ray intensity is then distributed between several irregular sequences. Different to other cases of band termination, the minimum in the total routhian surface corresponding to a collective shape is calculated to disappear in this spin region, although the available spin of the valence nucleons is far from being exhausted. A different structure, which is dominated by non-collective states becomes yrast.     

Improving results on transverse double spin asymmetries in the CNI region at STAR

Double spin effects in polarized pp-elastic scattering in the Coulomb nuclear interference (CNI) region are sensitive to small contributions to the nuclear amplitude in addition to Pomeron exchange dominating at high energies. Measurements of double spin asymmetries require external luminosity normalization using collision counts for all spin combinations. Several possible sources of such data from various STAR subsystems were thoroughly analyzed to make the best choice. BBC arrays were found to be free of double spin effects to the level of ～ 2 × 10^?4 thus leading to the systematic uncertainty ～10^?3 in the value of (A _NN + A _SS )/2.     

Spin-flip scattering effect on the current-induced spin torque in ferromagnet–insulator–ferromagnet tunnel junctions

We have investigated the current-induced spin transfer torque of a ferromagnet–insulator–ferromagnet tunnel junction by taking the spin-flip scatterings into account. It is found that the spin-flip scattering can induce an additional spin torque, enhancing the maximum of the spin torque and giving rise to an angular shift compared to the case when the spin-flip scatterings are neglected. The effects of the molecular fields of the left and right ferromagnets on the spin torque are also studied. It is found that τ^Rx/I_e (τ^Rx is the spin-transfer torque acting on the right ferromagnet and I_e is the tunneling electrical current) does vary with the molecular fields. At two certain angles, τ^Rx/I_e is independent of the molecular field of the right ferromagnet, resulting in two crossing points in the curve of τ^Rx/I_e versus the relevant orientation for different molecular fields.     

Theoretical evaluation of the electron paramagnetic resonance spin Hamiltonian parameters for the impurity displacements for Fe3+ and Ru3+ in corundum

The impurity displacements for Fe³⁺ and Ru³⁺ in corundum (Al₂O₃) are theoretically studied using the perturbation formulas of the spin Hamiltonian parameters (zero-field splitting and anisotropic g factors) for a 3d⁵ (with high spin S = 5/2) and a 4d⁵ (with low spin S = 1/2) ion in trigonal symmetry, respectively. According to the investigations, the nd⁵ (n = 3 and 4) impurity ions may not locate at the ideal Al³⁺ site but undergo axial displacements by about 0.132 Å and 0.170 Å for Fe³⁺ and Ru³⁺, respectively, away from the center of the ligand octahedron along the C₃ axis. The calculated spin Hamiltonian parameters based on the above axial displacements show good agreement with the observed values. The validity of the results is discussed.     

Manifestation of liquid-state and solid-state properties in electron relaxation of paramagnetic ions in solutions: Non-Markovian processes

The linewidth δH and the spin-spin relaxation time T ₂ for Gd³⁺, Mn²⁺, and Cr³⁺ ions in aqueous, water-glycerol, and water-poly(ethylene glycol) solutions at paramagnetic ion concentrations providing the dipole-dipole mechanism of spin relaxation are measured using two independent methods, namely, electron paramagnetic resonance (EPR) and nonresonance paramagnetic absorption in parallel fields. Analysis of the experimental results indicates a gradual crossover from pure liquid-state (diffusion) to quasi-solid-state (rigid lattice) spin relaxation. It is demonstrated that the limiting cases are adequately described by standard, universally accepted formulas for dipole-dipole interactions in the liquid-state (the correlation time of translational motion satisfies the condition τ _c ?τ₂) and solid-state (τ _c ?τ₂) approximations. A complete theoretical treatment of the experimental dependences (including the observed gradual crossover of spin relaxation) is performed in the framework of the non-Markovian theory of spin relaxation in disordered media, which is proposed by one of the authors. Within this approach, the collective memory effects for spin and molecular (lattice) variables are taken into account using the first-order and second-order memory functions for spin-spin and spin-lattice interactions. A correlation between the spin magnitude and the temperature-viscosity conditions corresponding to the crossover to non-Markovian relaxation is revealed, and the situations in which structural transformations occurring in the solutions favor the crossover to solid-state spin relaxation are analyzed.     

Crossover behavior of anisotropic cubic system with ionic anisotropy

Crossover behavior of anisotropic cubic N-component spin system with ionic anisotropies of different magnitude is studied in terms of the renormalization-group (RG) approach in momentum space. As a fundamental case, we choose a system with two kinds of strength of ionic anisotropies (i.e. m²₁ for the M-component spin and m²₂ for the other (N–M)-one), which has a bicritical point. We discuss the critical behavior and crossover behavior between the M- component system and the N-component system on the critical exponents [i.e., coefficient functions appearing in the RG equation of γS for the spin field S, γS² for the S²-field and γδS² for the δS² (≡[(N-M)S²₂-MS²₂]/N)-field] and on the temperature-dependent crossover exponent γeff.     

Study of Three-Quasiparticle Band in 83 Kr

Excited states of ⁸³Kr, populated in the ⁷⁶Ge(¹¹B, 3npγ) reaction at a beam energy of 50 MeV, have been studied. The ΔI?=?1 band, built upon the 2,510.0 keV state, has been observed up to 5,639.4 keV with spin (27/2^???). Mean lifetimes have been measured up to spin 23/2^?? in ΔI?=?1 band using the Doppler shift attenuation method. The B(M1) rates derived from the measured lifetimes decrease smoothly with spin indicating that the angular momentum belonging to this band are generated by the shears mechanism.     

The brute-force polarization of 23Na and the 23Na(n, γ)24Na reaction

A Na target has been polarized by brute force to 22% and the γ-radiation produced by polarized thermal neutron capture has been investigated. The J^π = 2⁺ channel spin contribution has been determined model-independently and unambiguously for 22 primary transitions. The average J^π = 2⁺ channel contribution is 5.8(5)%. The data resulted in one spin assignment and two spin restrictions. The energies and lifetimes of positive-parity levels as well as branching ratios and the magnetic moment of the ground state are in agreement with a shell-model calculation in the complete sd shell.     

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.     

Microscopic study of elastic 12C+16O scattering

The L=0 to 17 phase shifts are calculated microscopically for elastic ¹²C+¹⁶O scattering with a generator coordinate method. The experimental resonances are shown to belong to four different bands. Interpretations and spin assignments are suggested for several recently observed anomalies. A spin J=15 seems likely for the 22.8 MeV resonance. A missing J=13 resonance should be searched for between 17 and 18 MeV.     

Phenomenological simulation and density functional theory prediction of 57 Fe Mössbauer parameters: application to magnetically coupled diiron proteins

The use of phenomenological spin Hamiltonians and of spin density functional theory for the analysis and interpretation of Mössbauer spectra of antiferromagnetic or ferromagnetic diiron centers is briefly discussed. The spectroscopic parameters of the hydroxylase component of methane monooxygenase (MMOH), an enzyme that catalyzes the conversion of methane to methanol, have been studied. In its reduced diferrous state (MMOH _Red ) the enzyme displays ⁵⁷Fe Mössbauer and EPR parameters characteristic of two ferromagnetically coupled high spin ferrous ions. However, Mössbauer spectra recorded for MMOH _Red from two different bacteria, Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b, display slightly different electric quadrupole splittings (ΔE _Q ) in apparent contradiction to their essentially identical active site crystallographic structures and biochemical functions. Herein, the Mössbauer spectral parameters of MMOH _Red have been predicted and studied via spin density functional theory. The somewhat different ΔE _Q recorded for the two bacteria have been traced to the relative position of an essentially unbound water molecule within their diiron active sites. It is shown that the presence or absence of the unbound water molecule mainly affects the electric field gradient at only one iron ion of the binuclear active sites.     

The ground-state magnetic moments of odd-mass Hf isotopes

In this paper the Quasiparticle-Phonon Nuclear Model (QPNM), based on QRPA (Quasiparticle Random Phase Approximation) phonons, has been utilized to investigate spin polarization effects on the groundstate magnetic properties such as intrinsic magnetic moment (g _K ) and effective spin gyromagnetic factor (g _s ^eff. ) of odd-mass deformed ^165–179Hf isotopes with K > 1/2. Investigations of the spin polarization effects of the even core on the magnetic moments show that the spin gyromagnetic factors (g _s ) of the nucleons in the nucleus differ noticeably from the corresponding values for free nucleons and that the spin-spin interactions play an important role in the re-normalization of g _s factors of the odd-mass ^165–179Hf isotopes. In addition, some theoretical predictions are presented for the magnetic moments of ¹⁶⁵Hf, ¹⁶⁷Hf, and ¹⁶⁹Hf, whose ground state magnetic moments haven’t been experimentally determined yet.     

Spin Structure of the Nucleon at Low Q 2 Region

The spin structure of the nucleon can play a key testing ground for the Quantum Chromo-Dynamics(QCD) at wide kinematic ranges from smaller to large four momentum transfer Q ². It is far more challenging to understand the QCD at small Q ² region due to the non-perturbative nature. Jefferson Lab has been one of the major experimental facilities for the spin structure with its polarized electron beams and various polarized targets. A few QCD sum rules have been compared with the measured spin structure functions g ₁ and g ₂ at low Q ² and the most surprising results have been obtained for the spin polarizabilities, γ ₀ and δ _LT .