Chromium tracer diffusion in NiO crystals

Diffusion of ⁵¹Cr in NiO single crystals in air has been studied by the tracer-sectioning technique. In the temperature range 1192–1642°C, the diffusion coefficient can be expressed by the Arrhenius expression D=D_oexp(-Q/RT), with D_o=(8·6±1·2)×10^?3 cm²/sec and Q=67·4±1·1 kcal/mole. The use of a high specific-activity tracer and a special configuration for the diffusion anneal prevented the self-dopling effect found by Seltzer and the evaporation of chromium from the sample surface. The present results, in conjunction with published results on nickel self-diffusion in NiO and interdiffusion in the NiO?Cr₂O₃ system, are used to determine a chromium ion-vacancy binding energy of about 5 kcal/mole in pure NiO.     

Inelastic scattering studies on 50Cr

The inelastic scattering of protons, deuterons, τ and α from⁵⁰Cr has been studied. Spins, parities and transition strengths have been inferred for many states. The 1.89 MeV 4⁺state is excited by a double-excitation process, but more weakly than expected for a two-phonon state. A weak 5^? state is found at 4.37 MeV, and a 5⁺ state is inferred at 3.792 MeV.     

On sensitivity in optimal control problems

Two types of interpretations of multipliers in both static and dynamic optimization problems are described. It is snown that the Lagrange multipliers encountered in mathematical programming problems and the auxiliary functions arising in Pontryagintype optimal control problems sometimes have highly analogous interpretations as rates of change of the optimal attainable value of an objective function, or in some cases as bounds on average rates of change.     

The proton shell closure at 14C

Data for the ¹⁴C(³He, d)¹⁵N and ¹⁴C(t, ⁴He)¹³B reactions are compared to DWBA calculations to measure the spectroscopic factors for $\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{and}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ proton transitions. Good fits are found for the stripping data, as well as to similar stripping data on ¹²C. These results lower the previous value for proton $\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ hole strength in ¹⁴C by a factor of two, indicating that the neutron closure of the p-shell has provided a very good proton closed shell at ¹⁴C. Stripping results to low-lying positive parity states in ¹⁵N are interpreted within a Nilsson scheme, which reproduces the experimental results, but which requires a large deformation for the s-d orbitals.     

Branching fractions for psi(2S)-to-J/psi transitions

We describe new measurements of the inclusive and exclusive branching fractions for psi(2S) transitions to J/psi using e(+)e(-) collision data collected with the CLEO detector operating at CESR. All branching fractions and ratios of branching fractions reported here represent either the most precise measurements to date or the first direct measurements. Indirectly and in combination with other CLEO measurements, we determine B(chi(cJ) --> gamma(J/psi)) and B[psi(2S) --> light hadrons].     

Reconstructing the electron in a fractionalized quantum fluid

The low-energy physics of the fractional Hall liquid is described in terms of quasiparticles that are qualitatively distinct from electrons. We show, however, that a long-lived electronlike quasiparticle also exists in the excitation spectrum: the state obtained by the application of an electron creation operator to a fractional quantum Hall ground state has a nonzero overlap with a complex, high energy bound state containing an odd number of composite-fermion quasiparticles. The electron annihilation operator similarly couples to a bound complex of composite-fermion holes. We predict that these bound states can be observed through a conductance resonance in experiments involving a tunneling of an external electron into the fractional quantum Hall liquid. A comment is made on the origin of the breakdown of the Fermi liquid paradigm in the fractional Hall liquid.     

A search for the exotic Ξ<Superscript>−−</Superscript> (1860) in the hyperon beam experiment WA89(1860) in the hyperon beam experiment WA89

We report on a high statistics search for the Ξ^??(1860) resonance in Σ^?-nucleus collisions at 340 GeV/c. No evidence for this resonance is found in our data sample which contains 676000 Ξ^? candidates above bakground. For the decay channel Ξ^??(1860)→Ξ^? π ^? and the kinematic range 0.15<xF<0.9 we find a 3σ upper limit for the production cross section of 3.1 and 3.5 μb per nucleon, for reactions with carbon and copper, respectively.