Electrodeposited cobalt films: hcp versus fcc nanostructuring and magnetic properties

The crystallographic structure and morphology of electrodeposited cobalt films on Au(111) is found to be very sensitive on the electrolyte pH value and on the overpotential applied during deposition. The samples, 2 to 500 nm thick, where characterized by nuclear magnetic resonance (NMR), atomic force microscopy (AFM) and electron diffraction. The latter technique shows that the Co films grow in registry with the gold underlayer, reproducing the Au(111) texture. During the first stage of growth and depending on overpotential and pH value, either continuous hcp Co films or hcp Co islands are formed. Only the latter growth mode leads to an out of plane magnetization with 100% of remanence. Increasing the thickness, fcc Co becomes the prevailing phase. Eventually the fcc to hcp ratio saturates at the same value regardless the overpotential. The thickness for which the equilibrium fcc to hcp ratio is obtained as well as the sample structure and morphology before saturation, depend strongly on the overpotential value. In any case, the predominance of the fcc Co phase leads to an in plane magnetization of the thick samples. This study opens up new opportunities of engineering the properties of electrodeposited cobalt films. Received 29 February 2000 and Received in final form 3 July 2000     

Measurement of Lambda and Lambda(macro) particles in Au+Au collisions at the square root of S(NN) = 130 GeV

We present results on the measurement of Lambda and Lambda(macro) production in Au+Au collisions at square root of (S (NN) = 130 GeV with the PHENIX detector at the Relativistic Heavy Ion Collider. The transverse momentum spectra were measured for minimum bias and for the 5% most central events. The Lambda;/Lambda ratios are constant as a function of p(T) and the number of participants. The measured net Lambda density is significantly larger than predicted by models based on hadronic strings (e.g., HIJING) but in approximate agreement with models which include the gluon-junction mechanism.     

Flow measurements via two-particle azimuthal correlations in Au + Au collisions at sqrt [s(NN)]=130 GeV

Two-particle azimuthal correlation functions are presented for charged hadrons produced in Au+Au collisions at the Relativistic Heavy Ion Collider (sqrt [s(NN)]=130 GeV). The measurements permit determination of elliptic flow without event-by-event estimation of the reaction plane. The extracted elliptic flow values (v2) show significant sensitivity to both the collision centrality and the transverse momenta of emitted hadrons, suggesting rapid thermalization and relatively strong velocity fields. When scaled by the eccentricity of the collision zone epsilon, the scaled elliptic flow shows little or no dependence on centrality for charged hadrons with relatively low p(T). A breakdown of this epsilon scaling is observed for charged hadrons with pT >1.0 GeV/c.     

Redox sensing of anions in pure aqueous environment by ferrocene-containing 4,4'-bipyridinium-based receptors and polymer films

Selective voltammetric sensing of ATP(2-) anions in water was achieved using ferrocene-viologen based redox active receptors and related polymer films.     

Interferometry of direct photons in central 208Pb + 208Pb collisions at 158A GeV

Two-particle correlations of direct photons were measured in central 208Pb+208Pb collisions at 158A GeV. The invariant interferometric radii were extracted for 100相似文献   

Double helicity asymmetry in inclusive midrapidity pi0 production for polarized p+p collisions at square root s = 200 GeV

We present a measurement of the double longitudinal spin asymmetry in inclusive pi(0) production in polarized proton-proton collisions at sqrt[s]=200 GeV. The data were taken at the Relativistic Heavy Ion Collider with average beam polarizations of 0.27. The measurements are the first in a program to study the longitudinal spin structure of the proton, using strongly interacting probes, at collider energies. The asymmetry is presented for transverse momenta 1-5 GeV/c at midrapidity, where next-to-leading-order perturbative quantum chromodynamic (NLO pQCD) calculations well describe the unpolarized cross section. The observed asymmetry is small and is compared to a NLO pQCD calculation with a range of polarized gluon distributions.     

Nuclear modification factors for hadrons at forward and backward rapidities in deuteron-gold collisions at sqrt[s(NN)]=200 GeV

We report on charged hadron production in deuteron-gold reactions at sqrt[s(NN)]=200 GeV. Our measurements in the deuteron direction cover 1.4相似文献