336 research outputs found
Nuclear structure beyond the neutron drip line: the lowest energy states in He via their T=5/2 isobaric analogs in Li
The level structure of the very neutron rich and unbound He nucleus has
been the subject of significant experimental and theoretical study. Many recent
works have claimed that the two lowest energy He states exist with spins
and and widths on the order of hundreds of keV.
These findings cannot be reconciled with our contemporary understanding of
nuclear structure. The present work is the first high-resolution study with low
statistical uncertainty of the relevant excitation energy range in the
He system, performed via a search for the T=5/2 isobaric analog states
in Li populated through He+p elastic scattering. The present data show
no indication of any narrow structures. Instead, we find evidence for a broad
state in He located approximately 3 MeV above the neutron
decay threshold
The 8Li + 2H reaction studied in inverse kinematics at 3.15 MeV/nucleon using the REX-ISOLDE post-accelerator
The reaction 8Li + 2H has been studied in inverse kinematics at the incident energy of 3.15 MeV/nucleon, using the REX-ISOLDE post-accelerator. The reaction channels corresponding to (d,p), (d,d), and (d,t) reactions populating ground states and low-lying excited states in 7 -9Li have been identified and the related angular distributions extracted and compared with coupled-channels, distorted-wave Born approximation (DWBA), and coupled-reaction-channels calculations. For the inelastic and (d,t) channels we find that higher order effects are very important and hence one needs to go beyond the simple DWBA to extract reliable structure information from these processes.Ministerio de Ciencia e Innovación FPA2006-13807-C02-01 FPA2009-08848 FPA2009-07653 FPA2009-07387 FPA2010-17142Unión Europea RII3-EURONS 50606
Measurement of two-halo neutron transfer reaction p(Li,Li)t at 3 MeV
The p(\nuc{11}{Li},\nuc{9}{Li})t reaction has been studied for the first time
at an incident energy of 3 MeV delivered by the new ISAC-2 facility at
TRIUMF. An active target detector MAYA, build at GANIL, was used for the
measurement. The differential cross sectionshave been determined for
transitions to the \nuc{9}{Li} ground andthe first excited states in a wide
range of scattering angles. Multistep transfer calculations using different
\nuc{11}{Li} model wave functions, shows that wave functions with strong
correlations between the halo neutrons are the most successful in reproducing
the observation.Comment: 6 pages, 3 figures, submitted to Physical Review Letter
Initial operation of the recoil mass spectrometer EMMA at the ISAC-II facility of TRIUMF
The Electromagnetic Mass Analyser (EMMA) is a new vacuum-mode recoil mass spectrometer currently undergoing the final stages of commissioning at the ISAC-II facility of TRIUMF. EMMA employs a symmetric configuration of electrostatic and magnetic deflectors to separate the products of nuclear reactions from the beam, focus them in both energy and angle, and disperse them in a focal plane according to their mass/charge (m∕q) ratios. The spectrometer was designed to accommodate the γ-ray detector array TIGRESS around the target position in order to provide spectroscopic information from electromagnetic transitions. EMMA is intended to be used in the measurement of fusion evaporation, radiative capture, and transfer reactions for the study of nuclear structure and astrophysics. Its complement of focal plane detectors facilitates the identification of recoiling nuclei and subsequent recoil decay spectroscopy. Here we describe the facility and report on commissioning efforts
The role of the g9/2 orbital in the development of collectivity in the A = 60 region: The case of 61Co
An extensive study of the level structure of 61Co has been performed
following the complex 26Mg(48Ca, 2a4npg)61Co reaction at beam energies of 275,
290 and 320 MeV using Gammasphere and the Fragment Mass Analyzer (FMA). The
low-spin structure is discussed within the framework of shell-model
calculations using the GXPF1A effective interaction. Two quasi-rotational bands
consisting of stretched-E2 transitions have been established up to spins I =
41/2 and (43/2), and excitation energies of 17 and 20 MeV, respectively. These
are interpreted as signature partners built on a neutron {\nu}(g9/2)2
configuration coupled to a proton {\pi}p3/2 state, based on Cranked Shell Model
(CSM) calculations and comparisons with observations in neighboring nuclei. In
addition, four I = 1 bands were populated to high spin, with the yrast dipole
band interpreted as a possible candidate for the shears mechanism, a process
seldom observed thus far in this mass region
Evidence of a new state in Be observed in the Li -decay
Coincidences between charged particles emitted in the -decay of
Li were observed using highly segmented detectors. The breakup channels
involving three particles were studied in full kinematics allowing for the
reconstruction of the excitation energy of the Be states participating
in the decay. In particular, the contribution of a previously unobserved state
at 16.3 MeV in Be has been identified selecting the +
He + He+n channel. The angular correlations between the
particle and the center of mass of the He+n system favors spin and
parity assignment of 3/2 for this state as well as for the previously known
state at 18 MeV.Comment: 13 pages, 6 figure
Primordialists and Constructionists: a typology of theories of religion
This article adopts categories from nationalism theory to classify theories of religion. Primordialist explanations are grounded in evolutionary psychology and emphasize the innate human demand for religion. Primordialists predict that religion does not decline in the modern era but will endure in perpetuity. Constructionist theories argue that religious demand is a human construct. Modernity initially energizes religion, but subsequently undermines it. Unpacking these ideal types is necessary in order to describe actual theorists of religion. Three distinctions within primordialism and constructionism are relevant. Namely those distinguishing: a) materialist from symbolist forms of constructionism; b) theories of origins from those pertaining to the reproduction of religion; and c) within reproduction, between theories of religious persistence and secularization. This typology helps to make sense of theories of religion by classifying them on the basis of their causal mechanisms, chronology and effects. In so doing, it opens up new sightlines for theory and research
γ spectroscopy of states in Cl 32 relevant for the S 31 (p,γ) Cl 32 reaction rate
Background: The S31(p,γ)Cl32 reaction becomes important for sulfur production in novae if the P31(p,α)Si28 reaction rate is somewhat greater than currently accepted. The rate of the S31(p,γ)Cl32 reaction is uncertain, primarily due to the properties of resonances at Ec.m.=156 and 549 keV. Purpose: We precisely determined the excitation energies of states in Cl32 through high-resolution γ spectroscopy including the two states most important for the S31(p,γ)Cl32 reaction at nova temperatures. Method: Excited states in Cl32 were populated using the B10(Mg24,2n)Cl32 reaction with a Mg24 beam from the ATLAS facility at Argonne National Laboratory. The reaction channel of interest was selected using recoils in the Fragment Mass Analyzer, and precise level energies were determined by detecting γ rays with Gammasphere. Results: We observed γ rays from the decay of six excited states in Cl32. The excitation energies for two unbound levels at Ex=1738.1 (6) keV and 2130.5 (10) keV were determined and found to be in agreement with a previous high-precision measurement of the S32(He3,t)Cl32 reaction [1]. Conclusions: An updated S31(p,γ)Cl32 reaction rate is presented. With the excitation energies of important levels firmly established, the dominant uncertainty in the reaction rate at nova temperatures is due to the strength of the resonance corresponding to the 2131-keV state in Cl32
Reaction of the Halo Nucleus 11Be on Heavy Targets at Energies Around the Coulomb Barrier
New data for the reaction 11Be on 197Au at Elab=31.9 MeV are presented. The angular distributions of the inelastically scattered 11Be and the 10Be fragments coming from the 11Be dissociation have been extracted and compared with semiclassical and coupled-channels calculations in an angular range θlab=13∘–46∘ for the detected Be fragment.Ministerio de Ciencia e Innovación FPA2009-07387, FPA2009-07653, FPA2009-08848, FPA2012-32443 and CPAN CSD2007-00042Nuclear Astrophysics Virtual Institute (VH-VI-417
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