A new layered iron fluorophosphate

A new iron fluorophosphate of the composition, [C₆N₄H₂₁] [Fe₂F₂(HPO₄)₃][H₂PO₄]·2H₂O,I has been prepared by the hydrothermal route. This compound contains iron fluorophosphate layers and the H₂PO₄ ^- anions are present in the interlayer space along with the protonated amine and water molecules. The compound crystallizes in the monoclinic space group P2₁/c.(a = 13.4422(10) ?,b = 9.7320(10) ?, c = 18.3123(3) ?, β= 92.1480°,V= 2393.92(5) ?³, Z = 4,M = 719.92,d _calc. = 1.997 g cm^-3, R₁ = 0.03 andwR ₂= 0.09).     

Junction conditions at the boundary of a charged viscous-fluid sphere

Junction conditions are studied at the boundary of a sphere consisting of a charged viscous fluid with outgoing heat and radiation flux. The motion is anisotropic and the matching is done with the exterior Reissner-Nordström-Vaidya metric. A general relation in terms of the energy-momentum tensor componentsT ₁ ¹ andT ₄ ¹ is satisfied at the boundary hypersurface and this relation gives appropriate physical conditions in different special cases, some of which were obtained previously.     

Noise characteristics of a superlattice avalanche photodiode

The noise generated due to randomness of multiplication process in the avalanche region of an Al _x Ga_1–x As/GaAs quantum well p⁺-i-n⁺ structure has been studied. The paper presents a quantitative evaluation of the noise performance of the superlattice APD which has not been done so far. Further, useful design data for low noise structure is given.     

Transversity of quarks in a nucleon

The transversity distribution of quarks in a nucleon is one of the three fundamental distributions, that characterize nucleon's properties in hard scattering processes at leading twist (twist 2). It measures the distribution of quark transverse spin in a nucleon polarized transverse to its (infinite) momentum. It is a chiral-odd twist-two distribution function — gluons do not couple to it. Quarks in a nucleon/hadron are relativistically bound and transversity is a measure of the relativistic nature of bound quarks in a nucleon. In this work, we review some important aspects of this less familiar distribution function which has not been measured experimentally so far.     

Phase transition in triglycine family of hydrogen bonded ferroelectrics: An interpretation based on structural studies

Using the crystal structure, a comprehensive interpretation of the origin of ferroelectricity in the hydrogen bonded triglycine family of crystals is given. Our detailed analysis showed that the instability of nitrogen double well potential plays a driving role in the mechanism of the ferroelectric transitions in these crystals.     

Multiparameter study of 1H, 3H and 4He in fast neutron induced fission of 235U

The emission probabilities per fission of α-particles, tritons and protons have been measured in fast neutron induced fission of ²³⁵U. The measurements were carried out at neutron energies of 120, 180, 230 and 550 keV. AΔE-E semiconductor detector telescope was used to identify different light charged particles and the fission fragments were detected with an ionization chamber. The three-parameter data corresponding to the pulse heights from the ΔE-E detectors and the ion-chamber were recorded event by event on magnetic tape and were analyzed off-line by computer. No significant variation in the most probable energy ($\text{E}$) and the standard deviation (σ_E) of the energy spectra of different light charged particles with incident neutron energy was observed, although $\text{E}{}_{\mathrm{\alpha }}$ was seen to have a slightly higher value beyond E_n = 230 keV. The yield of α-particles in fission induced by neutrons of E_n ～ 200 keV was found to be higher by about 20 % than that in thermal neutron induced fission. The yields of tritons and protons were found to increase significantly with neutron energy.     

Light quark mass differences and charge symmetry breaking in hyperon-nucleon interaction

Quantum chromodynamics based isovector isoscolar particle mixing arising out of isospin violating quark mass differences has been used to construct a new charge-symmetry breaking Λ-N interaction element. It appears that vector meson exchanges between N and a physical Λ rather than pseudoscalar exchanges provide the largest contribution to explain the binding energy difference between the mirror hyper-nuclei _ΛHe⁴ and _ΛH⁴. Prediction of the model to Λn and Λp scattering lengths have been compared with those obtained from the combined analysis of ΛN scattering and s-shell hyperfragment data. We find satisfactory agreement of our results.     

Masses in structure functions

We derive an approximate formula for the quark mass in ξ-formalism. Using the QCD-based form of structure function, we analyse the SLAC-MIT data to estimate the experimentally allowed ranges of quark mass. The possible variation of our results with QCD cut-off parameter, gluon distribution, hard intrinsic charm component of the proton wavefunction and the higher twist effects are also discussed.     

Operator method and eigenvalues of the triple-well anharmonic oscillator

Using an algebraic technique based on the Lie algebra of the group SO(2, 1) the eigenvalues of the triple-well anharmonic oscillator are calculated for all ranges of the coupling constant. Approximate analytic formulas for the eigenvalues up to second order are given. The results obtained are compared with those of other authors.     

Anomaly in electron channeling due to imperfections produced thermally in a potassium chloride crystal

Lattice imperfections were produced in KCl crystals by a thermal process. The heat treated specimen was irradiated with 50 KeV electrons and the corresponding range of electrons in the crystal has been estimated. It was found that the electron range in the crystal depends upon the temperature of heat treatment, being a decreasing function of this temperature up to about 625 K, above which it becomes an increasing function. This anomaly has been explained in terms of dissolution of vacancies through dislocation loops.