Perturbed angular distribution of recoil implanted F19-nuclei in a nickel-environment

Magnetic hyperfine fields acting on F¹⁹ in a Nickel lattice have been investigated. Time-dependent spin rotation has been observed following the excitation and recoil implantation with a pulsed proton beam using the reaction F¹⁹(p,p′)F¹⁹?. Two hyperfine fields were detected at 290 °K:H _hf ⁽¹⁾ =+17.6 ± 0.5 kGH _hf ⁽²⁾ =+91 ± 3 kG. The variation of the effective fields with the external polarizing field was studied. The mean life of the 197 keV level has been remeasured as τ=128±2 nsec.     

Statistical parameters-based image enhancement techniques in pure and nanodispersed 6O.O8 liquid crystalline compounds

Synthesis, characterization and phase-transition studies in pure and 20?µl citrate-capped Au nanodispersed liquid crystalline (LC) N-(p-n-hexyloxybenzylidene)-p-n-octyloxy aniline, 6O.O8, compounds are carried out using a polarizing microscope attached with hot stage and camera. The polarizing microscopy technique is used to measure the phase-transition temperatures. Differential scanning calorimetry is used to determine the transition temperatures and enthalpy values. By the dispersion of citrate-capped Au nanoparticles into the LC compounds, the nematic transition temperature is decreased. Furthermore, statistical parameters-based image enhancement algorithm is proposed to identify the crystalline phases in the pure and nano-doped LC compound. Empirical result analysis clearly reveals the robustness of this method over existing image enhancement methods.     

Theoretical and experimental research on spectral performance and laser induced damage of Brewster's thin film polarizers

Polarizers respectively with broad polarizing region bandwidth, large layer thickness error tolerance and high extinction ratio are designed and prepared. Transmittance spectra of the prepared samples are measured at Brewster's angle, and the results show that different requirements can be fulfilled by optimized designs. Spectral performance of designs with higher layer thickness error tolerance coincides better with the theoretical spectra. Laser induced damage threshold of the prepared samples are evaluated. Electric field distribution, defect, film absorption, and damage morphology are investigated, and the results indicate that electric field distribution in high index layers is the main reason that causes the difference of laser induced damage threshold. For both p polarized and s polarized light, the lower the electric field peak value and the farther the layer, which has the strongest electric field away from air, the higher the laser induced damage threshold.     

Ultrasonic attenuation in the transverse spin density wave phase of chromium

A strong hysteretic attenuation peak is seen when a polarizing field itH_p is applied perpendicular to both the longitudinal ultrasonic wavevector itq and the wavevector itQ of the transverse spin density wave (TSDW) in chromium, i.e., itH_p⊥itq⊥ itQ, but not when (itH_p∥itq)⊥itQ. This effect is discussed in relation to the various models for the configuration of the polarization that have been proposed to explain the anomalous attenuation seen in the TSDW phase for itq⊥itQ.     

Polarizing optical behaviour of optically heterogeneous fibre-reinforced composites

This paper presents an investigation of the polarizing optical behaviour of fibre-reinforced composites with mismatched refractive indices. Because of their optical heterogeneous nature, these composites are very poor in transparency and do not present fringe patterns when examined under plane polariscopes. To overcome these difficulties, a Laser Microscopic Analyser (LMA) was developed. The polarizing optical behaviour of the target composites are represented in terms of the curves of transmitted light intensity versus azimuthal angle (I-θ curves). It was found that these curves are of an unequal-fold pattern; this cannot be described by the Jones calculus. Some of the factors were studied for their relationships with the special morphology of I-θ curves. The unequal-fold feature was found to exist independently from the optical arrangements of the LMA. Other factors, such as fibre content, temperature and especially stress in the composites had a strong influence on the change of I-θ patterns. The regular changes of these parameters lead to regular changes in the I-θ pattern. The strange I-θ patterns are, therefore, believed to be connected with the optically anisotropic nature of the optically heterogeneous fibre-reinforced composites. This work is considered to be an important step for the further attempt of establishing a transmissive photoelastic method for optically heterogeneous fibre-reinforced composites.     

A polarizing Michelson interferometer for the far-infrared and millimetre regions

A polarizing Michelson interferometer for the far-infrared and millimetre regions is described. It uses a simple mechanical drive to attain high-resolution spectra with excellent frequency accuracy, as evidenced by measurements of the rotational parameters for N₂O, for which the D parameter is measured with an uncertainty of ± 190 Hz; comparable with the accuracy of microwave techniques.     

Time-decay history of normal-deformation high-spin states in 193,194Hg

The time evolution of the decay of high-spin, normal deformed structures in ^193,194Hg was studied by measuring, in the Gammasphere array, the Doppler shift attenuation of selected transitions depopulating various bands. The data suggest that a fraction of states feeding selective yrast levels is non-collective in nature and show resemblance to A = 150 nuclei where shape polarizing effects have been linked to particles occupying high-j orbitals.     

The reaction 6Li (d, α)α with a new highly polarized 6Li target

A highly polarized ⁶Li target with a new polarizing principe has been developed. A surface is used to store polarized lithium particles from an atomic beam source. The maximum target tensor polarization is P_zz = 0.81 ± 0.06 and the thickness 3 × 10¹⁴ ions per cm².     

Magnetic properties of Mg1-pMnpTe2 near p = 0.5

Precise magnetization measurements and neutron diffraction measurements are carried out for Mg_1-pMn_pTe₂ near the critical concentration p = 0.5 for the antiferromagnetic ordering. A magnetization property which is similar to micto-magnetism is observed for p = 0.35 and p = 0.45 samples. The susceptibility shows an anomaly at T_f and field-cooling effect is notable below T_f. Neutron diffraction experiments show that most of the manganese moments are ordered antiferromagnetically for p = 0.53 while small fractions of Mn²⁺ are ordered for p = 0.45 and p = 0.35.     

Radiative constants in the spectra of ions of the krypton isoelectronic sequence

The probabilities of the 4p ⁶,4p ⁵5p→4p ⁵(4d+5s) radiative transitions and the radiative lifetimes of the 4p ⁵4d,4p ⁵5s, and 4p ⁵5p levels are calculated semiempirically for the RbII-MoVII isoelectronic sequence.     

Toroidal p-branes, anharmonic oscillators and (hyper)elliptic solutions

Exact solvability of brane equations is studied, and a new U(1)×U(1)×?×U(1) invariant anzats for the solution of p-brane equations in D=(2p+1)-dimensional Minkowski space is proposed. The reduction of the p-brane Hamiltonian to the Hamiltonian of p-dimensional relativistic anharmonic oscillator with the monomial potential of the degree equal to 2p is revealed. For the case of degenerate p-torus with equal radii it is shown that the p-brane equations are integrable and their solutions are expressed in terms of elliptic (p=2) or hyperelliptic (p>2) functions. The solution describes contracting p-brane with the contraction time depending on p and the brane energy density. The toroidal brane elasticity is found to break down linear Hooke law as it takes place for the anharmonic elasticity of smectic liquid crystals.     

Theoretical investigation on the ionic main and satellite states of some quinone and benzene like molecules: a search for low lying satellite states

The complete valence ionization spectra of p-quinodimethane, p-benzoquinone, p-quino-oxomethane, p-difluorobenzene and p-aminopyridine have been computed with an ab initio many-body Green's function method which includes the effect of electronic correlation and relaxation. Intense satellite line structure is found for all molecules and, for most of them, at very low energies. For the first three molecules, the satellite structure already affects the third, fourth and fifth main ionizations, respectively. For p-quinodimnethane this is a confirmation of earlier work. The inner valence spectra of all the molecules illustrate the breakdown of the molecular orbital picture of ionization. The assignment of the first four states of p-benzoquinone is also addressed and the ordering n₊, n₋, π₊, π₋ (with increasing binding energy) is obtained. The failure of Koopman's approximation in predicting the assignment of the first few ionization bands is also found for p-quinooxomethane and p-aminopyridine.     

Crossover scaling,correlation function and connectivity in dilute low temperature ferromagnets

For quenched dilute ferromagnets with a fractionp of spins (nearest neighbor exchange energyJ) and a fraction 1 —p of randomly distributed nonmagnetic atoms, a crossover assumption similar to tricritical scaling theory relates the critical exponents of zero temperature percolation theory to the low temperature critical amplitudes and exponents near the critical lineT _c (p)>0. For example, the specific heat amplitude nearT _c (p) is found to vanish, the susceptibility amplitude is found to diverge forT _c (p →p _c ) → 0. (Typically,p _c =20%.) AtT=0 the spin-spin correlation function is argued from a droplet picture to obey scaling homogeneity but (at fixed distance) not to vary like the energy; instead it varies as const + (p _c —p)^2β +? for fixed small distances. A generalization of the correlation function to finite temperatures nearT _c (p) allows to estimate the number of effective percolation channels connecting two sites in the infinite (percolating) network forp>p _c ; this in turn gives, via a dynamical scaling argument, a good approximation for theT=0 percolation exponent 1.6 in the conductivity of random three-dimensional resistor networks. This channel approximation also givesΦ=2 for the crossover exponent; i.e. exp(?2J/kT _c (p)) is an analytic function ofp nearp=p _c . An appendix shows that cluster-cluster correlations atT=0 (excluded volume effects) are responsible for the difference between percolation exponents and the (pure) Ising exponents atT _c (p=1).     

Temperature in Kaluza-Klein cosmologies

The temperature behavior is discussed for three typical equations of state in Kaluza-Klein cosmologies: (i) p = p′ = (λ − 1)ϱ, (ii) ϱ = − p = p′, (iii) ϱ = p = − p′.     

Line strengths and lifetimes for Kr II

Relative line strengths have been calculated for transitions between states of the 4p ⁴ 5p and 4p ⁴ 5s configurations in Kr II. The wavefunctions are obtained in intermediate coupling, including an effective correction for configuration interaction. Absolute values for the line strengths are determined using the coulomb approximation. Lifetimes for the upper 4p ⁴ 5p levels are given together with available experimental results for comparison.     

Proton-proton elastic scattering via the Trojan horse method

We address a successful indirect technique, the Trojan horse method, which allows one to measure the bare nucleus cross section for rearrangement reactions down to astrophysical energies. In particular, we consider here the application of the method to the p-p elastic scattering. This represents an important test of the main feature of the method, namely the suppression of Coulomb effects in the entrance channel due to off-energy-shell effects. In contrast to the on-energy-shell case, the extracted p-p cross section does not exhibit the Coulomb-nuclear interference minimum, as predicted by the half-off-energy shell calculations. This hypothesis is strengthened by the agreement between the Trojan horse p-p data and the calculated on-energy-shell n-n, n-p and nuclear p-p cross sections.     

Groundstate threshold in disordered anisotropic +/−J Ising models

In disordered anisotropic square +/− J Ising models SQ(p, q) at groundstates we investigate the pairs (p_c, q_c) of critical concentrations of antiferromagnetic bonds with concentrations p,q, respectively in orthogonal coordinate directions. We are led to p_c(q) ≈ π(q) with π(q) from the so-called adjoined problem. This approach is well supported by simulations for different values of q on the basis of minimal matchings of frustrated plaquettes. In particular, p_c(0) ≈ 0.21 from simulations and π(0) = 0.2113248 …, with the conjecture that p_c(0) = π(0). The concept of the adjoined problem is extended to d-dimensional (hyper-) cubic lattices. We hereby obtain for p_c,d especially in the sotropic case: p_c,3 ≈ 0.154, p_c,4 ≈ 0.170, p_c,5 ≈ 0.178, p_c,6 ≈ 0.182. Moreover, in analogy to SQ(p,q) we used the approach also for honeycomb Ising models HC(p,q,r) with no antiferromagnetic bonds in the third plaquette direction (r = 0).     

On the occurrence of an excitation-effect in pyromellitimide thin film

The effect of a preliminary illumination on the amount of polarization generated in the subsequently dark-polarized Kapton-H samples has been investigated by using the uv and visible radiations as an excitation source. The magnitude of this effect is governed by the two excitation parameters, viz. duration of the illumination (t _ex) and the time interval (Δt) between the end of illumination and the outset of the polarizing electric field. A rise in the operating temperature makes the appearance of the phenomenon more pronounced. The uv radiation has been found more efficient than the visible one for producing the excitation effect.     

Atomic parameters for carbon-like S XI

Radiative rates and collision strengths of S XI are presented for 46 levels of configurations 2s²2p², 2s2p³, 2p⁴, 2s²2p3s, 2s²2p3p, and 2s²2p3d.     

Tentatively identified and predicted H- Fano resonances

Positions are calculated for the Fano resonances that are due to interactions of the discrete autoionized 1s3s, 1s3p, and 1s4p states of H^- with overlapping split-configuration continua. The two first-mentioned resonances are tentatively identified with the diffuse interstellar doublets at λλ6376,6379 and λλ5780, 5797 on the basis of the relative positions of the autoionized states and the relative intensities of the doublet components.The observed wave-numbers of the 1s2s, 1s3s, 1s2p, and 1s3p resonances seem to belong to two series that converge towards a common limit in a kind of reverse Rydberg-series fashion. The position of the limit is close to 9000 Å, in accordance with theory. An extrapolation leads to the identification of the 1s4p resonance with the diffuse λ 6614 line. A further extrapolation leads to the prediction of positions at about 7183 and 7583 Å for the 1s5p and 1s6p resonances.The half-widths calculated for the singlet components of the 1s3p and 1s4p resonances are of the order of magnetude of those observed for the diffuse lines, and of the observed distance between the probably partly mixed singlet and triplet 1s3p components. The profile of the λ 5780 resonance is calculated on the basis of an assumed helium-line value for the oscillator strength. Its shape indicates that the “λ 5778 band” may be just a misinterpretation of the asymmetric wings.Tables of Hartree functions for the 3s², 3p² and 4p² configurations of H^- are given in an appendix.