Gamma radiolytic decomposition of solid binary mixtures of potassium nitrate with halides

Gamma-ray induced decomposition of solid binary mixtures of KNO₃ with halides viz. KCl, KBr and KI has been studied at room temperature. G(NO ₂ ^– ) values were found to vary with absorbed dose. Size and electronegativity of anions and molar composition of halides are the other factors influencing radiolysis.     

Collisional excitation of Na-Rydberg atoms

The scattering of heavy ion with a multilevel Rydberg atom in the presence of an electromagnetic field is studied. The interaction of Rydberg atom and the e.m field is explored using non-perturbative quasi-energy technique. Although the results are presented for selected excitations but in actual calculations we have included many levels of the atom. The effect of various parameters are shown on collisional excitation process. As an illustration detailed calculations are performed for the inelastic proton-Na Rydberg atom collision accompanied by the transfer of photons and the effects of dressing due to the field are considered. The emphasis of the present work is on collision induced transitions especially the case that involves change of orbital as well as principal quantum number. Received 26 December 2001 / Received in final form 8 April 2002 Published online 19 July 2002     

Investigating the mechanisms of diamond polishing using Raman spectroscopy

Recent research has shown that a phase transformation of diamond to a different form of carbon is involved when diamonds are polished in the traditional fashion. The question as to how this phase transformation is activated and maintained to produce high wear rates is of great technological interest since it may radically change the way we view the processing of diamond. This paper describes the use of Raman spectroscopy to examine debris produced on the diamond polishing wheel, both during its preparation and during polishing. In addition, polished diamond surfaces were examined for the possible existence of non-diamond surface layers in an attempt to identify material removal mechanisms. Raman spectroscopy proves ideal for these analyses because its relatively high spatial resolution is well suited to the analysis of small wear features and debris particles, and because of the wealth of information it reveals about chemical structure. This level of structural information has been lacking in previous analyses of diamond polishing debris. In addition to the non-diamond carbon found in the wear debris, significant quantities of two iron oxides, magnetite (Fe₃O₄) and haematite (α-Fe₂O₃), were also found. An interesting observation was that a transformation from magnetite to haematite could be induced either by using high power laser excitation or by frictional heating during polishing. It is suggested that some of the Raman peaks previously attributed to lonsdaleite might better be explained by the presence of these oxides.     

Magnetic behavior of amorphous Fe−Ni−Zr alloys and their response to radiation damage

The magnetic properties of two amorphous Fe?Ni?Zr alloys, Fe_89.7Ni_0.03Zr₁₀ and Fe₇₀Ni₂₀Zr₁₀, both in the “as cast” and neutron irradiated states were investigated by Mössbauer spectroscopy and dc magnetic susceptibility measurements. The upper magnetic ordering temperatures of Fe_89.7Ni_0.03Zr₁₀ are 232K and 246K for the “as cast” and irradiated samples, respectively. The magnetic ordering temperature for Fe₇₀Ni₂₀Zr₁₀ was about 478K for both the “as cast” and irradiated samples. Both compositions yield magnetic hyperfine spectra, which show a considerable relaxation effect that must be explicitly considered in the calculation of the average local Fe moments. When this is done, these values derived from Mössbauer spectra are in good agreement with the dc susceptibility values. The effects of neutron irradiation on the magnetic properties of these alloys are small.     

The force on a lattice defect in an elastic body

It is shown that the force on a lattice defect in an elastic body is, like the force on a disclination in a nematic liquid crystal, a real force which, for equilibrium, must be balanced by an external force applied to the closed surface enclosing the defect.     

Hydroxy(tosyloxy)iodo]benzene mediated alpha-azidation of ketones

Reaction of various ketones with [hydroxy(tosyloxy)iodo]benzene (HTIB) followed by treatment of the alpha-tosyloxy ketones thus generated in situ with NaN3 offers a one-pot procedure for the synthesis of alpha-azido ketones. The HTIB used in this conversion may also be generated in situ by using iodosobenzene in combination with p-toluene-sulphonic acid.