1,022 research outputs found
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
Positron-neutrino correlations in 32Ar and 33Ar Decays: Probes of Scalar weak currents and nuclear isospin mixing
The positron-neutrino correlation in the 0^+ \to 0^+ \beta decay of ^{32}Ar
was measured at ISOLDE by analyzing the effect of lepton recoil on the shape of
the narrow proton group following the superallowed decay. Our result is
consistent with the Standard Model prediction; for vanishing Fierz interference
we find a=0.9989 \pm 0.0052 \pm 0.0036. Our result leads to improved
constraints on scalar weak interactions. The positron-neutrino correlation in
^{33}Ar decay was measured in the same experiment; for vanishing Fierz
interference we find a=0.944 \pm 0.002 \pm 0.003. The ^{32}Ar and ^{33}Ar
correlations, in combination with precision measurements of the half-lives,
superallowed branching ratios and beta endpoint energies, will determine the
isospin impurities of the superallowed transitions. These will provide useful
tests of isospin-violation corrections used in deducing |V_{\rm ud}| which
currently indicates non-unitarity of the KM matrix.Comment: 15 pages, 6 figure
Systematic trends in beta-delayed particle emitting nuclei: The case of beta-p-alpha emission from 21Mg
We have observed beta+-delayed alpha and p-alpha emission from the
proton-rich nucleus 21Mg produced at the ISOLDE facility at CERN. The
assignments were cross-checked with a time distribution analysis. This is the
third identified case of beta-p-alpha emission. We discuss the systematic of
beta-delayed particle emission decays, show that our observed decays fit
naturally into the existing pattern, and argue that the patterns are to a large
extent caused by odd-even effects.Comment: 6 pages, 5 figure
Oxalis loricata Dusén
Patagonia australis, Cerro Toro, supra terminum silvaepublishedVersio
Clarification of the low-lying states of Be-9
5 pages, 1 table, 2 figures.-- Presented at the
International Conference on Finite Fermionic Systems: Nilsson Model 50 years (Lund University, Sweden, June 14–18, 2005).--
PACS nrs.: 23.40.Hc, 27.20.+n, 24.80.+y.A newly developed technique for dealing with three-body decays of broad isolated levels is extended to deal with the broad, overlapping levels found at 2-9 MeV excitation energy in Be-9. The levels are populated through beta-decay of Li-9. The method gives firm evidence for the existence of several levels. Angular correlation studies allow spin values to be assigned.Peer reviewe
Nuclear structure of Ac-231
The low-energy structure of 231Ac has been investigated by means of gamma ray
spectroscopy following the beta-decay of 231Ra. Multipolarities of 28
transitions have been established by measuring conversion electrons with a
mini-orange electron spectrometer. The decay scheme of 231Ra --> 231Ac has been
constructed for the first time. The Advanced Time Delayed beta-gamma-gamma(t)
method has been used to measure the half-lives of five levels. The moderately
fast B(E1) transition rates derived suggest that the octupole effects, albeit
weak, are still present in this exotic nucleus
Beta-delayed deuteron emission from 11Li: decay of the halo
The deuteron-emission channel in the beta-decay of the halo-nucleus 11Li was
measured at the ISAC facility at TRIUMF by implanting post-accelerated 11Li
ions into a segmented silicon detector. The events of interest were identified
by correlating the decays of 11Li with those of the daughter nuclei. This
method allowed the energy spectrum of the emitted deuterons to be extracted,
free from contributions from other channels, and a precise value for the
branching ratio B_d = 1.30(13) x 10-4 to be deduced for E(c.m.) > 200 keV. The
results provide the first unambiguous experimental evidence that the decay
takes place essentially in the halo of 11Li, and that it proceeds mainly to the
9Li + d continuum, opening up a new means to study of the halo wave function of
11Li.Comment: 4 pages, 3 figure
Shapes of the Pb ground states from beta decay studies using the total absorption technique
The beta decay of Pb has been studied using the total absorption
technique at the ISOLDE(CERN) facility. The beta-decay strength deduced from
the measurements, combined with QRPA theoretical calculations, allow us to
infer that the ground states of the Pb isotopes are spherical.
These results represent the first application of the shape determination method
using the total absorption technique for heavy nuclei and in a region where
there is considerable interest in nuclear shapes and shape effects
Study of bound states in 12Be through low-energy 11Be(d,p)-transfer reactions
The bound states of 12Be have been studied through a 11Be(d,p)12Be transfer
reaction experiment in inverse kinematics. A 2.8 MeV/u beam of 11Be was
produced using the REX-ISOLDE facility at CERN. The outgoing protons were
detected with the T-REX silicon detector array. The MINIBALL germanium array
was used to detect gamma rays from the excited states in 12Be. The gamma-ray
detection enabled a clear identification of the four known bound states in
12Be, and each of the states has been studied individually. Differential cross
sections over a large angular range have been extracted. Spectroscopic factors
for each of the states have been determined from DWBA calculations and have
been compared to previous experimental and theoretical results
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