Nuclei are complex quantum objects due to complex nucleon-nucleon interactions. They can undergo rather rapid changes in structure as a function of nucleon number. A well known region of such a shape ...transition is the rare-earth region around N = 90, where accessible nuclei range from spherical nuclei at the closed neutron shell at N = 82 to deformed nuclei. For a better understanding of this phenomenon, it is of interest to study empirical signatures like the E2 transition strength \(B(E2;{2}_{1}^{+}\to {0}_{1}^{+})\) or the E0 excitation strength \({\rho }^{2}(E0;{0}_{1}^{+}\to {0}_{2}^{+})\). The nuclide 152Gd with 88 neutrons is located close to the quantum phase transition at N = 90. The lifetime \(\tau ({0}_{2}^{+})\) of 152Gd has been measured using fast electronic scintillation timing (FEST) with an array of HPGe- and LaBr3- detectors. Excited states of 152Gd were populated via an (α,n)-reaction on a gold-backed 149Sm target. The measured lifetime of \(\tau ({0}_{2}^{+})=96(6)\text{ps}\) corresponds to a reduced transition strength of \(B(E2;{0}_{2}^{+}\to {2}_{1}^{+})=111(7)\) W.u. and an E0 transition strength of ρ 2(E0) = 39(3) · 10−3 to the ground state. This result provides experimental support for the validity of a correlation between E0 and E2 strengths that is a novel indicator for a quantum phase transition. This work was published as J. Wiederhold et al., Phys. Rev. C 94, 044302 (2016).
The excitation spectra in the deformed nucleus 232U have been studied by means of the (p, t) reaction. 0+ assignments for 13 excited states and up to spin 6+ for other states are made from the ...angular distributions of tritons and the coupled-channel approximation analysis. Sequences of states are selected which can be treated as rotational bands. Moments of inertia have been derived from these sequences, whose values may be considered as evidence of the two- or one-phonon nature of these 0+ excitations. Experimental data are compared with interacting boson model (IBM) and quasiparticle-phonon model (QPM) calculations.
In this contribution, further evidence of the importance of multiphonon-octupole excitations to describe experimental data in the rare earths and actinides will be presented. First, new results of a ...(p, t) experiment at the Q3D magnetic spectrograph in Munich will be discussed, which was performed to selectively excite Jπ = 0+ states in 240Pu. spdf interacting boson model (IBM) calculations suggest that the previously proposed double-octupole phonon nature of the Jπ = 0+2 state is not in conflict with its strong (p, t) population. Second, the framework of the IBM has been adopted for the description of experimental observables related to octupole excitations in the rare earths. Here, the IBM is able to describe the signature splitting for positiveand negative-parity states when multi-dipole and multi-octupole bosons are included. The present study might support the idea of octupole-phonon condensation at intermediate spin (Jπ = 10+) leading to the change in yrast structure observed in 146Nd.
In this paper, we investigate the problem of all-to-all broadcast in optical networks, also known as gossiping. This problem is very important in the context of control plane design as it relates to ...status information dissemination. We present a routing and wavelength assignment (RWA) method to reduce the number of wavelengths such that the communication is conflict-free in a wavelength division multiplexing (WDM) optical environment without wavelength converters. Our approach utilizes the tap-and-continue capability of the optical nodes. The network topology is considered to be arbitrary as long as it is connected. Both cases of maximally and nonmaximally edge-connected graphs are studied. For the first case, we give a closed-form expression for the lower bound on the number of wavelengths, which is an elegant extension of the results in for concurrent broadcast trees in optical networks. Furthermore, we show how to achieve this bound. The second case is more involved and requires a specific procedure to achieve the minimum number of wavelengths. For this case, we provide an attractive method for the RWA algorithm that attempts to minimize the number of wavelengths. Our solution for this case is within a constant factor that is strictly less than 2 from the optimal solution. The proposed algorithm uses the concept of "cactus" representation of all minimum edge-cuts in a graph in a novel recursive approach.
Beta-delayed proton emission from 20Mg Lund, M. V.; Andreyev, A.; Borge, M. J. G. ...
The European physical journal. A, Hadrons and nuclei,
2016, Letnik:
52, Številka:
10
Journal Article
Recenzirano
Odprti dostop
.
Beta-delayed proton emission from
20
Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station (IDS) setup including both charged-particle and gamma-ray detection capabilities. A total of ...27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in
20
Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State (IAS) in
20
Na is observed. This may allow studies of the 4032.9(2.4)keV resonance in
19
Ne through the beta decay of
20
Mg, which is important for the astrophysically relevant reaction
15
O(
,
)
19
Ne . Beta-delayed protons were used to obtain a more precise value for the half-life of
20
Mg, 91.4(1.0)ms.
This paper reviews the research in progress in Oxford on the chemical, spectroscopic and redox properties of bis(thiosemicarbazonato) complexes of zinc and copper in the context of the hypoxia ...selectivity of the copper(II) complex. Also, covered are synthetic strategies for modified complexes with a range of functional substituents and the in vitro and in vivo characteristics of two of these derivatives are described. Finally, the synthesis of some new bifunctional macrocyclic ligands is described and some of these give Cu(II) derivatives which cannot be reduced and are therefore resistant to reductive loss of copper in vivo.
We report on a gamma-ray coincidence analysis using a mixed array of hyperpure germanium and cerium-doped lanthanum tri-bromide (LaBr3:Ce) scintillation detectors to study nuclear electromagnetic ...transition rates in the pico-to-nanosecond time regime in 33,34P and 33S following fusion–evaporation reactions between an 18O beam and an isotopically enriched 18O implanted tantalum target. Energies from decay gamma-rays associated with the reaction residues were measured in event-by-event coincidence mode, with the measured time difference information between the pairs of gamma-rays in each event also recorded using the ultra-fast coincidence timing technique. The experiment used the good full-energy peak resolution of the LaBr3:Ce detectors coupled with their excellent timing responses in order to determine the excited state lifetime associated with the lowest lying, cross-shell, Iπ=4− “intruder” state previously reported in the N=19 isotone 34P. The extracted lifetime is consistent with a mainly single-particle M2 multipolarity associated with a f7/2→d5/2 single particle transition.
► Half-life measurements of nuclear states. ► Using fast-timing properties of (LaBr3:Ce) scintillator detectors. ► (LaBr3:Ce) scintillation detectors have an excellent timing resolution.
It is shown for the first time that the ASCSTS technique we have introduced several years ago for lifetime measurements can be also used for measuring low level activities. A good example with ...practical relevance in this respect is
90
Sr isotope. In order to apply this technique the radioactive isotope must have an isomeric state with a lifetime spanning the ns–μs range. This method is adequate for measuring weak activities with high detection efficiency in a geometry close to 4π. It is experimentally demonstrated that ASCSTS method is a reliable, high efficiency technique for measuring absolute radioactivity in the long radioactive chains.
It is shown for the first time that the ASCSTS technique we have introduced several years ago for lifetime measurements can be also used for measuring low level activities. A good example with ...practical relevance in this respect is sup.90Sr isotope. In order to apply this technique the radioactive isotope must have an isomeric state with a lifetime spanning the ns-micros range. This method is adequate for measuring weak activities with high detection efficiency in a geometry close to 4pi. It is experimentally demonstrated that ASCSTS method is a reliable, high efficiency technique for measuring absolute radioactivity in the long radioactive chains. Keywords Radioactive sources * Autocorrelation single-crystal scintillation time spectrometer * Weak radioactivity * Lifetime measurement
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