The PbPb collision

The reaction ²⁰⁸Pb on ²⁰⁸Pb was studied at bombarding energies of 7.0 and 7.57 MeV/u. One-particle inclusive measurements using a large-area position-sensitive ionisation chamber delivered the kinetic energy, charge and scattering angle of the reaction products. A precise calibration of the stopping power for very heavy ions in the detector gas was performed. The measured Wilczynski diagrams show, for increasing loss of kinetic energy, an increase of the mean scattering angle. It is attributed to the dominance of the repulsive Coulomb forces with respect to the attractive nuclear forces. The element distribution for the ²⁰⁸Pb on ²³⁸U reaction at 7.5 MeV/u was also measured and compared to the PbPb and UU reactions. Fission probabilities are derived as a function of charge and total kinetic energy loss. The most striking result is seen in the σ_z² versus TKEL correlation: the average rate of energy loss per nucleon exchange is abnormally large. It is shown that this behaviour is associated with the double magic closed shell character of the colliding nuclei. Nuclear structure information is extracted through a simple parametrisation.     

K-X-ray spectrum of the Pb + Pb quasimolecules

We present ab initio calculations of the quasimolecular K-X-ray spectrum from the Pb + Pb system, where both the Kd-hole amplitude and the radiation amplitude is calculated in first order perturbation theory. A comparison with the background radiation like NNB, SEB and γ-decay of excited nuclei shows that the molecular X-rays should be measurable up to X-ray energies corresponding to the characteristic K-line of the united superheavy atom.     

Superconductivity of Pb films studied with superconducting Pb tips

<正>Studying the superconductivity of materials using scanning tunneling microscopy (STM) remains a challenge to this day[1]. In this regard, the stability of the tunneling junction is a critical factor, together with the spectroscopy resolution.Using a superconducting tip is an effective way to increase the resolution of the obtained tunneling spectra [2-6]. For example, Pan et al.[2] showed that the use of super-     

Particle production in Pb+Pb collisions at the SPS

Experiment NA49 at the CERN SPS employs a large acceptance detector to study particle spectra, yields and correlations in nucleus-nucleus, nucleon-nucleus and nucleon-nucleon collisions. Preliminary results on pion, kaon, A and ā production in central Pb+Pb collisions at 40, 80 and 158 A·GeV beam energy are shown and compared to measurements at lower and higher energies.     

High-spin levels in the 199Pb and 200Pb isotopes

The de-excitation of the ²⁰⁰Pb and ¹⁹⁹Pb isotopes, produced through the ¹⁸⁶W(¹⁸O,4n, 5n) reactions, is investigated using γ-ray and conversion electron spectroscopy. The conversion coefficients are measured and the multipolarities deduced for a great number of transitions. The e⁻γ- and γγ-coincidences and the half-life measurements lead to several new levels in both level schemes; the ²⁰⁰Pb one is extended up to nearly 7 MeV, where an isomer is found. The experimental results are compared to those of microscopic calculations, performed in a two or three quasi-particle approximation, using a surface delta interaction with a reduced pairing component.     

Selective observation of continuum transitions in the Pb+Pb quasimolecule

Cross sections for doubleK shell excitation and for the production of continuum x-rays in coincidence withK x-rays from 4.8 MeV/amu²⁰⁸Pb +²⁰⁸Pb collisions have been measured. A simple statistical model is presented to explain double vacancy contributions to the coincidence cross sections and the relative contributions of MO x-ray,K x-ray cascade and MO x-ray,K x-ray double vacancy coincidences are evaluated. These latter yields are found to be significant enough to make extraction of the cascade contribution to the measured coincidence yields problematic.     

Andreev-reflection in highly doped Pb/n−InSb/Pb junctions

We studied the carrier transport through n-InSb-films sandwiched between two superconducting lead electrodes. These n-InSb-films were about 30 nm thick, polycrystalline and very highly doped (10²¹ cm^–3). TheV(I)- and dV/dI (V)-characteristics indicated all the properties of Andreev-reflection (subharmonic energygap structures (SGS) and excess current) according to the theory of Octavio et al. (OTBK-model) [1, 2]. Our measurements show the temperature dependence of these structures and also the influence of magnetic fields up to 80 mT and give a further reference to the importance of Andreev-reflection in semiconductor-coupled superconducting junctions (SSmS junctions).     

Identification of180Pb

Theα decay of the new isotope¹⁸⁰Pb was observed in⁴⁰Ca bombardments of¹⁴⁴Sm:E _α = 7.23(4)MeV, and,T _1/2=(4 _?2 ⁺⁴ )ms. With this decay energy and the known mass of¹⁷⁶Hg, the mass excess of¹⁸⁰Pb was calculated to be ?1.98(5)MeV.     

Antideuteron production in 158A GeV/c Pb + Pb collisions

The invariant cross section as a function of transverse momentum for antideuterons produced in 158A GeV/c per nucleon Pb+Pb central collisions has been measured by the NA44 experiment at CERN. This measurement, together with a measurement of antiprotons, allows for the determination of the antideuteron coalescence parameter. The extracted coalescence radius is found to agree with the deuteron coalescence radius and radii determined from two particle correlations.     

Relativistic many-electron SCF correlation diagram for superheavy quasimolecules: PbPb

We present the first relativistic many-electron SCF correlation diagram for a superheavy quasimolecule: PbPb. The discussion shows a large number of quantitative as well as qualitative differences as compared with the known one-electron correlation diagram.     

Tribochemical reduction of Pb in Pb containing glazes: An ESCA investigation

Most white glazes, used in the ceramics industry for the coating of tiles, show deep, black scratches after tribological treatment with other glazes. Contrary to similar scratches produced during scraping with metals, these failures cannot be removed by polishing. ESCA investigations on Pb containing transparent and white glazes have shown unambiguously that during the tribological treatment the Pb in the surface of the glaze is partially reduced to metallic Pb which could at least partially explain the deep, black scratches seen on the tiles after the treatment.     

Superdeformation in194Pb

High spin states in the odd- odd nucleus¹²⁴Cs have been investigated within theNordball collaboration. In the yrast cascade which is determined as a πh_11/2 ? νh_11/2 configuration, a rather large signature splitting in the ratios, B(M1)/B(E2), has been observed. Furthermore, signature inversion is suggested in the lower spin part of the yrast band.     

Fluctuation conductivity in Pb

The electrical conductivity of two-dimensional lead films was measured above T_c. Deviations from the Aslamozov and Larkin theory are small, and the data cannot be fit to Patton's theory, perhaps because the theory applies to weak coupling superconductors.     

New isotope184Pb

The new isotope¹⁸⁴Pb has been produced through⁴⁰Ca +^147,148Sm reactions, and detected by its a radioactivity (E_α = 6618 ± 10 keV). The detection technique involves thermalization of recoil nuclei in a gas and electrostatic collection onto the active surface of a solid state detector. The identification is made on the basis of the (⁴⁰Ca,xn) excitation functions, and of the time correlation with the α-decay of the daughter¹⁸⁰Hg.     

Photodisintegration of Pb isotopes

Yields of photonucleon reactions of different multiplicity of natural isotopic mixture of Pb were measured on a bremsstrahlung photon beam with a maximum energy of 67.7 MeV using gamma-activation methods. Cross-sections of photonucleon reactions of different multiplicity were calculated on stable Pb isotopes within the bounds of the combined model. The calculated cross sections are compared to those measured in experiments on quasimonochromatic photon beams. They are also used to split the measured yields into yields of particular photonucleon reactions.     

Identification of 180Pb

The α decay of the new isotope ¹⁸⁰Pb was observed in ⁴⁰Ca bombardments of ¹⁴⁴Sm: E _α = 7.23(4) MeV, and, \({T_{1/2}} = \left( {4_{ - 2}^{ + 4}} \right){\text{ ms}}\) . With this decay energy and the known mass of ¹⁷⁶Hg, the mass excess of ¹⁸⁰Pb was calculated to be ?1.98(5) MeV.