Absorption and refraction phenomena in proton- and antiproton-nucleus scattering

The experimental data on the 180 MeV proton and 50, 180 MeV antiproton scattering by the nuclei¹²C,⁴⁰Ca and²⁰⁸Pb have been analysed on the basis of the phenomenological diffraction theory. The optical properties of the nuclei with regards to the incident protons and antiprotons are investigated. Various limiting cases of the proton- and antiproton-nucleus scattering are considered. The contribution of the Coulomb and the spin-orbit interactions to the differential cross sections of these processes has been also analysed.The authors are indebted to D.M. Skrypnik for assistance in preparing the English version of this paper.     

Isotonic and isobaric dependencies of nuclear charge radii for rare-earth nuclei

Isotonic and isobaric dependencies of nuclear charge radii in the region between Z=54 and Z=70 are obtained from the analysis of isotope shift data r² and muonic and electron scattering data on r². They are compared with the predictions of the droplet model and the Hartree-Fock calculations. The isobaric dependencies of r² have proven to be especially sensitive to the choice of an effective nucleon-nucleon interaction.     

Investigations of correlated ρ+ e− emission in heavy-ion collisions near the Coulomb barrier

We present the results obtained from a series of ^+–-coincidence measurements in heavy-ion collisions using the double-Orange-spectrometer at GSI. The collision systems U+U, U+Pb, and U+Ta were investigated at bombarding energies close to and slightly above (U+Ta) the Coulomb barrier. For all systems studied, very narrow (FWHM–20 keV) ^+– lines were observed in the sum-energy spectra, with kinetic energies ranging from 555 keV to 810 keV, superimposed on a continuous distribution mainly due to uncorrelated ^+– emission. Particularly in the U+Ta system, a pronounced sum-energy line appears at 634 keV, predominantly in deep-inelastic collisions. In some cases (e.g. U+Pb) the line characteristics is consistent with a two-body decay mode of an emitter which moves with the c.m. velocity of the colliding ions. However, other lines, and in particular the 634 keV line (U+Ta), exhibit a rather isotropical opening-angle distribution whereas their energy is unequally shared between positrons and electrons, thus being in clear disagreement with this scenario. In general, the data preclude an emission from the separated (moving) nuclei, and, in the latter cases, provide evidence that the e⁺e^–-pair decay occurs in the vicinity of the Coulomb field of a third heavy (positively charged) partner having only a small transverse velocity (|v|<>Dedicated to Prof. B. Povh on the occasion of his 60th birthday     

Multi-strange systems in relativistic mean fields

Characteristics of multi- hypernuclei are investigated within the relativistic mean-field theory. Both linear and nonlinear models and a variety of couplings fitted to ordinary hypernuclei have been investigated. All the parametrizations used in the present work predict qualitatively similar dependence of the studied quantities (rms radii, binding energies, densities) on a number of hyperons.Deceased on May 5, 1991     

Two-proton multiplets in theN=82 nucleus 62 144 Sm82 from in-beamγ-measurements

In a high sensitivity (,2n) in-beam study of ₆₂ ¹⁴⁴ Sm₈₂, with the Kölner Würfel OSIRIS -detector array including a Compton polarimeter, we have identified the complete two-proton multiplets d ₅ ^2/–2 , d ₅ ^2/–1 g ₇ ^2/–1 , g ₇ ^2/–2 , h_11/2d ₅ ^2/–1 and the 9^– to 4^– members of the h_11·/2g ₇ ^2/–1 multiplet.Work partially supported by CICYT (Spain).     

On the mechanism of the N,N‐dimethyl amination of Grignard reagents: a kinetic study

A direct kinetic study is reported for the electrophilic amination of substituted phenylmagnesium bromides with N,N‐dimethyl O‐(mesitylenesulfonyl)hydroxylamine in THF. Rate data, Hammett relationship, and activation entropy are consistent with a S_N2 displacement involving the attack of carbanions to sp³N in the amination reagent (AR). Copyright © 2007 John Wiley & Sons, Ltd.     

Oxygen defect dependent variation of band gap,Urbach energy and luminescence property of anatase,anatase–rutile mixed phase and of rutile phases of TiO2 nanoparticles

TiO₂ nanoparticles are prepared by a sol–gel method and annealed both in air and vacuum at different temperatures to obtain anatase, anatase–rutile mixed phase and rutile TiO₂ nanoparticles. The phase conversion from anatase to anatase–rutile mixed phase and to rutile phase takes place via interface nucleation between adjoint anatase nanocrystallites and annealing temperature and defects take the initiate in this phase transformation. The samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis and photoluminescence spectroscopy (PL). Anatase TiO₂ exhibits a defect related absorption hump in the visible region, which is otherwise absent in the air annealed samples. The Urbach energy is very high in the vacuum annealed and in the anatase–rutile mixed phase TiO₂. Vacuum annealed anatase TiO₂ has the lowest emission intensity, whereas an intense emission is seen in its air annealed counterpart. The oxygen vacancies in the vacuum annealed samples act as non-radiative recombination centers and quench the emission intensity. Oxygen deficient anatase TiO₂ has the longest carrier lifetime. Time resolved spectroscopy measurement shows that the oxygen vacancies act as efficient trap centers of electrons and reduce the recombination time of the charge carriers.     

Electronic properties of anatase TiO2 doped by lanthanides: A DFT+U study

The effects of mono-doping of 4f lanthanides with and without oxygen vacancy defect on the electronic structures of anatase TiO₂ have been studied by first-principles calculations with DFT+U (DFT with Hubbard U correction) to treat the strong correlation of Ti 3d electrons and lanthanides 4f electrons. Our results revealed that dopant Ce is easy to incorporate into the TiO₂ host by substituting Ti due to its lower substitutional energy (∼−2.0 eV), but the band gap of the system almost keeps intact after doping. The Ce 4f states are located at the bottom of conduction band, which mainly originates from Ti 3d states. The magnetic moment of doped Ce disappears due to electron transfer from Ce to the nearest O atoms. For Pr and Gd doping, their substitutional energies are similar and close to zero, indicating that both of them may also incorporate into the TiO₂ host. For Pr doping, some 4f spin-down states are located next to the bottom of the conduction band and narrow the band gap of the doping system. However, for Gd doping, the 4f states are located in deep valence band and there is no intermediate band in the band gap. The magnetic moment of dopant Gd is close to the value of isolated Gd atom (∼7 μB), indicating no overlapping between Gd 4f with other orbitals. For Eu, it is hard to incorporate into the TiO₂ host due to its very higher substitutional energy. The results also indicated that oxygen vacancy defect may enhance the adsorption of the visible light in Ln-doped TiO₂ system.     

Analysis of Ωb? (bss) and Ωc0 (css) with QCD sum rules

We calculate the masses and the pole residues of the heavy baryons Ω _c ⁰(css) and Ω _b ⁻(bss) with the QCD sum rules. The numerical values  GeV (or  GeV) and  GeV (or  GeV) are in good agreement with the experimental data.     

Analysis of non-photonic electrons in Cu + Cu collisions at $\sqrt{s_{NN}}=200$ GeV

Heavy-flavor semileptonic decays are expected to dominate the spectrum of non-photonic electrons produced from collisions at the energies of the Relativistic Heavy Ion Collider. The non-photonic electron yield is suppressed by approximately a factor of 5 in central Au + Au events at  GeV relative to p+p events with the same collision energy. Most theoretical models predict less non-photonic-electron suppression than is observed experimentally. We present a preliminary measurement of the yield of non-photonic electrons in Cu + Cu events at  GeV, as well as the nuclear modification factor.