122 research outputs found
Spectroscopy of neutron-unbound F
The ground state of F has been observed as an unbound resonance
keV above the ground state of F. Comparison of this
result with USDA/USDB shell model predictions leads to the conclusion that the
F ground state is primarily dominated by -shell configurations. Here
we present a detailed report on the experiment in which the ground state
resonance of F was first observed. Additionally, we report the first
observation of a neutron-unbound excited state in F at an excitation
energy of keV.Comment: 10 pages, 11 figures, Accepted for publication in Phys. Rev.
Observation of a low-lying neutron-unbound state in 19C
Proton removal reactions from a secondary 22N beam were utilized to populate
unbound states in neutron-rich carbon isotopes. Neutrons were measured with the
Modular Neutron Array (MoNA) in coincidence with carbon fragments. A resonance
with a decay energy of 76(14) keV was observed in the system 18C+n
corresponding to a state in 19C at an excitation energy of 653(95)keV. This
resonance could correspond to the first 5/2+ state which was recently
speculated to be unbound in order to describe 1n and 2n removal cross section
measurements from 20C.Comment: accepted for publication in Nucl. Phys.
Structure and Decay Correlations of Two-Neutron Systems Beyond the Dripline
The two-neutron unbound systems of 16Be, 13Li, 10He, and 26O have been measured using the Modular Neutron Array (MoNA) and 4 Tm Sweeper magnet setup. The correlations of the 3-body decay for the 16Be and 13Li were extracted and demonstrated a strong correlated enhancement between the two neutrons. The measurement of the 10He ground state resonance from a 14Be(−2p2n) reaction provided insight into previous predictions that wavefunction of the entrance channel, projectile, can influence the observed decay energy spectrum for the unbound system. Lastly, the decay-in-target (DiT) technique was utilized to extract the lifetime of the 26O ground state. The measured lifetime of 4.5+1.1 −1.5 (stat.)±3(sys.) ps provides the first indication of two-neutron radioactivity
Exploring the Low- Shore of the Island of Inversion at
The technique of invariant mass spectroscopy has been used to measure, for
the first time, the ground state energy of neutron-unbound
determined to be a resonance in the continuum at
keV. States in were
populated by the reactions of a 62 MeV/u beam impinging on a
288 beryllium target. The measured ground
state energy is in good agreement with USDA/USDB shell model predictions,
indicating that shell intruder configurations play only a small role in
the ground state structure of and establishing a low-
boundary of the island of inversion for N=19 isotones.Comment: 5 pages, 4 figures, to be published in Phys. Rev. Let
Observation of Ground-State Two-Neutron Decay
Neutron decay spectroscopy has become a successful tool to explore nuclear
properties of nuclei with the largest neutron-to-proton ratios. Resonances in
nuclei located beyond the neutron dripline are accessible by kinematic
reconstruction of the decay products. The development of two-neutron detection
capabilities of the Modular Neutron Array (MoNA) at NSCL has opened up the
possibility to search for unbound nuclei which decay by the emission of two
neutrons. Specifically this exotic decay mode was observed in 16Be and 26O.Comment: To be published in Acta Physica Polonica
Exploring the neutron dripline two neutrons at a time: The first observations of the 26O and 16Be ground state resonances
The two-neutron unbound ground state resonances of O and Be
were populated using one-proton knockout reactions from F and B
beams. A coincidence measurement of 3-body system (fragment + n + n) allowed
for the decay energy of the unbound nuclei to be reconstructed. A low energy
resonance, 200 keV, was observed for the first time in the O + n + n
system and assigned to the ground state of O. The Be ground state
resonance was observed at 1.35 MeV. The 3-body correlations of the Be +
n + n system were compared to simulations of a phase-space, sequential, and
dineutron decay. The strong correlations in the n-n system from the
experimental data could only be reproduced by the dineutron decay simulation
providing the first evidence for a dineutron-like decay.Comment: Invited Talk given at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
Women, anger, and aggression an interpretative phenomenological analysis
This study reports a qualitative phenomenological investigation of anger and anger-related aggression in the context of the lives of individual women. Semistructured interviews with five women are analyzed using interpretative phenomenological analysis. This inductive approach aims to capture the richness and complexity of the lived experience of emotional life. In particular, it draws attention to the context-dependent and relational dimension of angry feelings and aggressive behavior. Three analytic themes are presented here: the subjective experience of anger, which includes the perceptual confusion and bodily change felt by the women when angry, crying, and the presence of multiple emotions; the forms and contexts of aggression, paying particular attention to the range of aggressive strategies used; and anger as moral judgment, in particular perceptions of injustice and unfairness. The authors conclude by examining the analytic observations in light of phenomenological thinking
Microscopy techniques for determining water-cement (w/c) ratio in hardened concrete: A round-robin assessment
Water to cement (w/c) ratio is usually the most important parameter specified in concrete design and is sometimes the subject of dispute when a shortfall in concrete strength or durability is an issue. However, determination of w/c ratio in hardened concrete by testing is very difficult once the concrete has set. This paper presents the results from an inter-laboratory round-robin study organised by the Applied Petrography Group to evaluate and compare microscopy methods for measuring w/c ratio in hardened concrete. Five concrete prisms with w/c ratios ranging from 0.35 to 0.55, but otherwise identical in mix design were prepared independently and distributed to 11 participating petrographic laboratories across Europe. Participants used a range of methods routine to their laboratory and these are broadly divided into visual assessment, measurement of fluorescent intensity and quantitative backscattered electron microscopy. Some participants determined w/c ratio using more than one method or operator. Consequently, 100 individual w/c ratio determinations were collected, representing the largest study of its type ever undertaken. The majority (81%) of the results are accurate to within ± 0.1 of the target mix w/c ratios, 58% come to within ± 0.05 and 37% are within ± 0.025. The study shows that microscopy-based methods are more accurate and reliable compared to the BS 1881-124 physicochemical method for determining w/c ratio. The practical significance, potential sources of errors and limitations are discussed with the view to inform future applications
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