A Short,Convenient Synthesis of 2-Arylglycidates via Aryl-Grignard Addition to an α-Bromopyruvate

A simple procedure has been developed for the preparation of a series of 2-arylglycidates required for herbicidal evaluation. Treatment of the α-bromopyruvate 5 with various aryl Grignard reagents at low temperature gave directly the glycidates 4. Saponification of these then afforded the desired sodium salts 7.     

The role of 14N and 13C hyperfine structure in characterizing point defects in diamond

Hyperfine structure (hfs), of either ¹³C or ¹⁴N, observed in the electron paramagnetic resonance (EPR) spectrum, has been a remarkably powerful indicator of the models of paramagnetic defects in diamond. It has often been valuable or necessary to use the much higher resolution of electron nuclear double resonance (ENDOR). Measurements of hfs have recently allowed considerable progress in understanding the nature of defects which have been uncharacterized for many years. A rich variety of defects involving up to at least 4 N atoms, which readily substitute for C atoms, has been found in diamond. The role of ¹⁴N hfs is reviewed in solving problems where different aspects are relevant. The use of synthetic diamond, enriched by up to 10% in ¹³C, has greatly facilitated the construction of models for centres produced by radiation damage, where the only information is from ¹³C hfs. Both ¹⁴N and ¹³C hfs have confirmed models of Ni related centres. This revised version was published online in August 2006 with corrections to the Cover Date.     

Quantum action-angle variables for harmonic oscillators

The well-known difficulties of defining a phase operator of an oscillator, caused by the lower bound on the number operator, is overcome by enlarging the physical Hilbert space by means of a spin-like, two-valued quantum number. On the enlarged space a phase representation exists on which trigonometric functions of the phase are numbers, and the “number of quanta” is a differential operator. Physical results are recovered by projection on the “upper components.” Coherent states, indeterminacy relations, as well as generalizations to other Hamiltonians, including the quantum analog of the quasi-periodic case, are discussed.     

Overcomplete multicenter basis sets

The distribution of eigenvalues of the overlap matrix is analyzed for large and, in the limit, infinite overcomplete multicenter basis sets. It is shown that in the limit the eigenvalues become infinitely degenerate. A numerical example is given and discussed in terms of a semiclassical distribution in phase space.     

Photoproduction of ω mesons from complex nuclei targets

Measurements are presented of the cross sections for omega meson photoproduction at a mean energy of 3.9 GeV from nuclear targets of D, Be, C, Al, Cu, Ag, Au. An optical and Glauber model analysis of the coherent cross sections has been performed to obtain the ω-nucleon cross section, σ_ωN, and the photon-omega coupling constant γ_ω²/4π. Our results are summarised in table 4. We find good agreement with the quark model prediction that σ_ωN = σ_?N, and with the value of γ_ω2/4π determined from the storage ring experiments and from an earlier complex nuclei measurement. However, we disagree with more recent complex nuclei measurements which found a high value of γ_ω²/4π.     

Nitrogen in diamond studied by magnetic resonance

Nitrogen is the most common substitutional impurity in diamond. Much of the information about the many different defects in diamond containing nitrogen atoms has been found by magnetic resonance. This information is reviewed, and the possibility is discussed of finding information about more such centres, mechanisms of their formation and alteration by external influences. The unambiguously identified centres involve either: (a) only substitutional nitrogen atoms, up to three in number, (b) a combination, of substitutional nitrogen atoms and vacancies, (c) substitutional nitrogen and other foreign atoms. Speculations are made about the atomic models of less well characterized centres, as well as about some simple possible centres which have not yet been identified.     

Rotational bands in the light odd-mass Tl nuclei

The odd-mass nuclei ^191–197Tl have been formed in a variety of (HI, xn) reactions and studied by in-beam spectroscopic techniques. The decay of the high-spin Pb isomers, also formed in (HI, xn) reactions, leading to ^193–197Tl has also been investigated. Evidence is presented for the existence of levels of the previously proposed $\text{9}\text{2}{}^{\mathrm{?}}\text{[505]}$rotational bands in the nuclei. Tentative evidence is given for the existence of oblate rotational bands, based on the $\text{13}\text{2}{}^{\mathrm{+}}\text{[606]}$ state, in ^191–195Tl.