Search results for " CLUSTER"
showing 10 items of 2162 documents
Collisional and thermal ionization of sodium Rydberg atoms III. Experiment and theory fornS andnD states withn= 8–20 in crossed atomic beams
2005
The results of experimental and theoretical studies of collisional ionization of Na Rydberg atoms in nS and nD(n = 8–20) states are presented. Molecular and atomic ions from associative ionization and photoionization by blackbody radiation were detected after pulsed laser excitation of Rydberg states in crossed Na atomic beams. An original method of determination of associative ionization rate constants based on the measurement of ratios of molecular and atomic ion signals was used, which did not require the determination of absolute number density of Rydberg atoms. The measured rate constants of associative ionization of Rydberg atoms in collisions with ground-state Na atoms are compared w…
Direct Bound on the Total Decay Width of the Top Quark inpp¯Collisions ats=1.96 TeV
2009
We present the first direct experimental bound on the total decay width of the top quark, Gamma(t), using 955 pb(-1) of the Tevatron's p (p) over bar collisions recorded by the Collider Detector at Fermilab. We identify 253 top-antitop pair candidate events. The distribution of reconstructed top quark mass from these events is fitted to templates representing different values of the top quark width. Using a confidence interval based on likelihood-ratio ordering, we extract an upper limit at 95% C.L. of Gamma(t) < 13.1 GeV for an assumed top quark mass of 175 GeV/c(2).
Theoretical overview on top pair production and single top production
2012
In this talk I will give an overview on theoretical aspects of top quark physics. The focus lies on top pair production and single top production.
Top-quark pair production cross-section measurements with the ATLAS detector
2019
Measurements of the inclusive and differential top-quark pair production cross sections in proton-proton collisions with the ATLAS detector at the Large Hadron Collider at center-of-mass energies of 8 TeV and 13 TeV are presented. The inclusive measurements reach high precision and are compared to the best available theoretical calculations. Differential measurements of the kinematic properties of the top-quark production are also discussed. These measurements, including results using boosted tops, probe our understanding of top-quark pair production in the TeV regime.
Measurement of Top Quark Polarization in Top-Antitop Events from Proton-Proton Collisions ats=7 TeVUsing the ATLAS Detector
2013
This Letter presents measurements of the polarization of the top quark in top-antitop quark pair events, using 4: 7 fb(-1) of proton-proton collision data recorded with the ATLAS detector at the La ...
Shell-like structures in our cosmic neighbourhood
2016
Signatures of the processes in the early Universe are imprinted in the cosmic web. Some of them may define shell-like structures characterised by typical scales. We search for shell-like structures in the distribution of nearby rich clusters of galaxies drawn from the SDSS DR8. We calculate the distance distributions between rich clusters of galaxies, and groups and clusters of various richness, look for the maxima in the distance distributions, and select candidates of shell-like structures. We analyse the space distribution of groups and clusters forming shell walls. We find six possible candidates of shell-like structures, in which galaxy clusters have maxima in the distance distribution…
Mixed-Valence Magnetic Molecular Cell for Quantum Cellular Automata: Prospects of Designing Multifunctional Devices through Exploration of Double Exc…
2020
In this article, we propose to use multielectron square-planar mixed-valence (MV) molecules as molecular cells for quantum cellular automata (QCA) devices. As distinguished from previous proposals ...
Photoelectron spectra from first principles: from the many-body to the single-particle picture
2008
We derive a many-body method to evaluate photoelectron spectra of atoms, molecules and clusters from first principles. The excitation energies and the spectroscopic factors are calculated from the linear-response time-dependent density functional theory. The method is applied to noble metal anions, anionic clusters and to neutral small molecules. Our approach shows significant improvement over a simple single-particle treatment and gives an insight into the necessary conditions under which the single-particle picture holds. The consideration of the spectroscopic factor is shown to be crucial for the correct description of inner valence photoelectron peaks.
Shell structure in mixed3He−4Hedroplets
2004
Due to the immiscibility of ${}^{3}\mathrm{He}$ into ${}^{4}\mathrm{He}$ at very low temperatures, mixed helium droplets consist of a core of ${}^{4}\mathrm{He}$ atoms coated by a ${}^{3}\mathrm{He}$ layer whose thickness depends on the number of atoms of each isotope. When these numbers are such that the centrifugal kinetic energy of the ${}^{3}\mathrm{He}$ atoms is small and can be considered as a perturbation to the mean-field energy, a novel shell structure arises, with magic numbers different from these of pure ${}^{3}\mathrm{He}$ droplets. If the outermost shell is not completely filled, the valence atoms align their spins up to the maximum value allowed by the Pauli principle.
Quantum chemical simulations of hole self-trapping in semi-ionic crystals
1994
A novel formalism is presented for reliable calculations of the energetics of hole self-trapping in semi-ionic solids with mixed valence bands. Unlike previous model-Hamiltonian-type approaches, it is based on self-consistent quantum chemical INDO simulations of the atomistic and electronic structure of a self-trapped hole, making no a priori assumptions about a particular form of its localization (if any). This formalism is applied to the problem of hole self-trapping in corundum crystals (a -A1203). The hole self-trapping is found to be energetically favorable in the form of a diatomic 02 molecule with strong covalent bonding quite similar to the self-trapped hole (VK-center) in alkali ha…