Search results for "nucleus"
showing 10 items of 1803 documents
In-beam study of low-lying levels in the149Sm nucleus
1989
The146Nd(α,n) reaction combined with conventional in-beam spectroscopic methods has been used to study low-lying levels in149Sm. Several new levels andγ-ray transitions have been placed to the149Sm level scheme. Main features of levels below 1 MeV in149Sm have been reproduced in a quasiparticle-rotor model calculation.
Systematic study of the single-state dominance in 2νββ decay transitions
1999
Abstract The single-state-dominance hypothesis (SSDH) states that the decay rates of the two-neutrino double-beta decay are governed by a virtual two-step transition connecting the initial and final ground states through the first 1 + state, 1 l + , of the intermediate odd-odd nucleus, for those odd-odd nuclei where the 1 l + state is the ground state. To investigate the validity of the SSDH we have performed a systematical theoretical analysis of all known double-beta-decay transitions where the SSDH conditions are fulfilled. the calculations are based on the quasiparticle random-phase approximation (QRPA) and the results have been obtained by using realistic single-particle bases and real…
Lifetime measurements probing triple shape coexistence in ^{175}Au
2011
Lifetimes of the low-lying excited states in the very neutron-deficient nucleus ${}^{175}$Au have been measured by the recoil-distance Doppler-shift method using $\ensuremath{\gamma}$-ray spectra obtained with the recoil-decay tagging technique. Transition quadrupole moments and reduced transition probabilities extracted for this odd-$Z$ nucleus indicate the existence of three different shapes and the competition between collective and noncollective structures.
Quasielastic K-nucleus scattering
1996
Quasielastic K^+ - nucleus scattering data at q=290, 390 and 480 MeV/c are analyzed in a finite nucleus continuum random phase approximation framework, using a density-dependent particle-hole interaction. The reaction mechanism is consistently treated according to Glauber theory, keeping up to two-step inelastic processes. A good description of the data is achieved, also providing a useful constraint on the strength of the effective particle-hole interaction in the scalar-isoscalar channel at intermediate momentum transfers. We find no evidence for the increase in the effective number of nucleons participating in the reaction which has been reported in the literature.
First observation of excited states of173Hg
2012
The neutron-deficient nucleus 173Hg has been studied following fusion-evaporation reactions. The observation of gamma rays decaying from excited states are reported for the first time and a tentative level scheme is proposed. The proposed level scheme is discussed within the context of the systematics of neighbouring neutron-deficient Hg nuclei. In addition to the gamma-ray spectroscopy, the alpha decay of this nucleus has been measured yielding superior precision to earlier measurements.
Signatures of oblate deformation in the ^{111}Tc nucleus
2011
Monoisotopic samples of exotic, neutron-rich ${}^{111}$Mo nuclei, produced in the deuteron-induced fission of ${}^{238}$U and separated using the IGISOL3 isotope separator, coupled to the JYFLTRAP Penning trap, were used to perform $\ensuremath{\beta}$- and $\ensuremath{\gamma}$-coincidence spectroscopy of ${}^{111}$Tc. New excited levels in ${}^{111}$Tc populated in ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of ${}^{111}$Mo provide the first indication for an oblate deformation in the mass $A\ensuremath{\approx}110$ region. The wide spin range of levels populated in ${}^{111}$Tc following the decay of ${}^{111}$Mo indicates the existence of two $\ensuremath{\beta}$-decaying levels in ${…
Proton emission from an oblate nucleus 151Lu
2013
Abstract Excited states in the proton-unbound nucleus 151Lu have been established using γ-ray coincidence techniques. The lifetime of the first excited state above the proton-emitting ground state has been measured using the recoil-distance Doppler-shift method combined with recoil-decay tagging. The experimental level scheme and extracted lifetime have been compared with state-of-the-art theoretical calculations based upon a non-adiabatic deformed Woods–Saxon potential. This comparison suggests that the proton-emitting ground state in 151Lu is mildly oblate with a deformation β = − 0.11 − 0.05 + 0.02 and represents the best evidence to date for proton emission from an oblate nucleus.
Investigation of the Δn = 0 selection rule in Gamow-Teller transitions: The β-decay of 207Hg
2019
5 pags., 3 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0
Collective features of Cr and Fe isotopes
2014
The question of the sudden increase of collectivity in neutron-rich nuclei when approaching $N=40$ has recently interested both experimentalists and theorists. In this paper we study the development of collectivity along the chromium and iron isotopic chains. The calculations are performed within two different perspectives, namely, the proton-neutron interacting boson model (IBM-2) and interacting shell model (ISM) and compared with the available experimental data. The onset of collectivity is studied through nuclear quantities and observables that suggest differences in the nuclear structure of Cr and Fe isotopical chains. Furthermore, a prediction for the shape transition from a spherical…
Low energy collective modes of deformed superfluid nuclei within the finite amplitude method
2013
Background: The major challenge for nuclear theory is to describe and predict global properties and collective modes of atomic nuclei. Of particular interest is the response of the nucleus to a time-dependent external field that impacts the low-energy multipole and beta-decay strength. Purpose: We propose a method to compute low-lying collective modes in deformed nuclei within the finite amplitude method (FAM) based on the quasiparticle random-phase approximation (QRPA). By using the analytic property of the response function, we find the QRPA amplitudes by computing the residua of the FAM amplitudes by means of a contour integration around the QRPA poles in a complex frequency plane. Metho…