Search results for "Reaction"
showing 10 items of 6134 documents
Attempts to Produce Superheavy Elements by Fusion ofCa48withCm248in the Bombarding Energy Range of 4.5-5.2 MeV/u
1985
A search for superheavy elements was made in bombardments of $^{248}\mathrm{Cm}$ with $^{48}\mathrm{Ca}$ ions performed at projectile energies close to the interaction barrier in order to keep the excitation energy of the compound nucleus $Z=116$, $A=296$ as low as possible. No evidence for superheavy nuclei was obtained in a half-life region from 1 \ensuremath{\mu}s to 10 yr with a production cross section greater than ${10}^{\ensuremath{-}34}$ to ${10}^{\ensuremath{-}35}$ ${\mathrm{cm}}^{2}$.
First Exploration of Neutron Shell Structure below Lead and beyond N=126
2020
The nuclei below lead but with more than 126 neutrons are crucial to an understanding of the astrophysical r process in producing nuclei heavier than A∼190. Despite their importance, the structure and properties of these nuclei remain experimentally untested as they are difficult to produce in nuclear reactions with stable beams. In a first exploration of the shell structure of this region, neutron excitations in ^{207}Hg have been probed using the neutron-adding (d,p) reaction in inverse kinematics. The radioactive beam of ^{206}Hg was delivered to the new ISOLDE Solenoidal Spectrometer at an energy above the Coulomb barrier. The spectroscopy of ^{207}Hg marks a first step in improving our…
New High-Precision Measurement of the Reaction Rate of the 18O(p, α)15N Reaction via THM
2008
The 18O(p,alpha)15N reaction rate has been extracted by means of the Trojan-Horse method. For the first time the contribution of the 20-keV peak has been directly evaluated, giving a value about 35% larger than previously estimated. The present approach has allowed to improve the accuracy of a factor 8.5, as it is based on the measured strength instead of educated guesses or spectroscopic measurements. The contribution of the 90-keV resonance has been determined as well, which turned out to be of negligible importance to astrophysics.
Production and Characterization of the $^{7}$H Resonance
2006
Détecteur MAYA; International audience; The 7H resonance was produced via one-proton transfer reaction between a 8He beam at 15.4A MeV and a 12C gas target. The experimental setup was based on the active-target MAYA which allowed a complete reconstruction of the reaction kinematics. The characterization of the identified 7H events resulted in a resonance energy of 600 keV above the 3H+4n threshold and a resonance width of 100 keV. This study represents the first unambiguous proof of the existence of the 7H state.
FARCOS, a new array for femtoscopy and correlation spectroscopy
2012
Correlations between two or more particles can be used as a tool to explore the space-time features of nuclear reactions as well as spectroscopic properties of produced unbound clusters. In order to have new options to study the mentioned correlations, FARCOS (Femtoscope ARray for COrrelations and Spectroscopy) has been conceived as a compact high resolution array, composed of square telescopes. In this work the main features of FARCOS array as well as part of the physics cases are described. © Owned by the authors, 2012.
Oscillation Phenomena Leading to Chaos in a Stochastic Surface Reaction Model
1998
A microscopic lattice gas model for the $\mathrm{CO}+\mathrm{NO}$ reaction on Pt(100) is studied by means of Monte Carlo simulations. It shows different kinetical phenomena such as steady state reaction, damped, regular, and irregular oscillations, as well as a transition into chaotical behavior via the Feigenbaum route. Because of its small number of parameters, each with a specific physical meaning, it enables the investigation of the whole parameter regime leading to a deeper insight to the mechanisms which create the oscillations and chaotical behavior.
Quantum mechanical study of the 16O + 18O18O → 16O18O + 18O exchange reaction: Integral cross sections and rate constants
2018
The isotopic exchange reaction, 16O + 18O18O → 16O18O + 18O, involving excited ozone, O3*, as intermediate complex, was investigated by means of a time independent quantum mechanical approach using the TKTHS potential energy surface (PES) [V. G. Tyuterev et al., J. Chem. Phys. 139, 134307 (2013)] of ozone. State-to-state integral cross sections were calculated for collision energies lower than 0.4 eV. Then specific and thermal rate constants were computed between 10 K and 350 K using these cross sections. The full quantum thermal rate constant is found to be in better agreement with the most recent experimental data than with previous studies where other O3 PESs were employed, confirming th…
On the dynamics of dislocation patterning
1997
Recent computer simulations on dislocation patterning have provided remarkable results in accordance with empirical laws. Moreover, several analytical models on dislocation dynamics have provided qualitative insight on dislocation patterning. However, a model, based on partial differential equations, which gives a dynamical evolution of dislocation patterns in function of measurable variables still missing. Here, we give a re-formulation of a model proposed some years ago. From this formulation, we obtained that the onset of a dislocation instability is related to the applied stress. The analytical and numerical results reported are partial and studies on this direction are under developmen…
Recent Developments in one and two Pion Production in Elementary Reactions and Few-Body Systems
1995
In this talk we cover several issues concerning pion production. The first one is the pp → ppπ 0 reaction where an alternative explanation based on the off shell extrapolation of the πN amplitude is offered. A recent model for the γN → ππN reaction is presented and a new kind of exchange current is constructed from it which allows one to address problems like double ∆ photoproduction from the deuteron. Finally the (γ, ππ) reaction in nuclei is studied and shown to be highly sensitive to the renormalization of the pions in nuclei.
Equivalence between local Fermi gas and shell models in inclusive muon capture from nuclei
2005
Motivated by recent studies of inclusive neutrino nucleus processes and muon capture within a correlated local Fermi gas model (LFG), we discuss the relevance of nuclear finite size effects in these reactions at low energy, in particular for muon capture. To disentangle these effects from others coming from the reaction dynamics we employ here a simple uncorrelated shell model that embodies the typical finite size content of the problem. The integrated decay widths of muon atoms calculated with this shell model are then compared for several nuclei with those obtained within the uncorrelated LFG, using in both models exactly the same theoretical ingredients and parameters. We find that the t…