Search results for "quasiparticle"
showing 10 items of 280 documents
Neutrino scattering off the stable cadmium isotopes: neutral-current processes
2014
In this work we present computed cross sections for the incoherent neutral-current neutrino scattering off the stable cadmium isotopes. The main focus is on supernova neutrinos. The nuclear states of the even-mass and odd-mass cadmium isotopes have been constructed using the quasiparticle random-phase approximation and the microscopic quasiparticle-phonon model, respectively. The computed cross sections are folded with suitably parametrized Fermi–Dirac distributions of the supernova (anti)neutrinos energies to obtain realistic estimates of the nuclear responses to these neutrinos.
Collective 2$^{+1}$ excitations in$^{206}$Po and$^{208,210}$Rn
2016
In the present study, $B(E2; 2^{+}_{1}\rightarrow 0^{+}_{1})$ values have been measured in the 208,210Rn and 206Po nuclei through Coulomb excitation of re-accelerated radioactive beams in inverse kinematics at CERN-ISOLDE. These nuclei have been proposed to lie in, or at the boundary of the region where the seniority scheme should persist. However, contributions from collective excitations are likely to be present when moving away from the N=126 closed shell. Such an effect is confirmed by the observed increased collectivity of the $2^{+}_{1}\rightarrow 0^{+}_{1}$ transitions. Experimental results have been interpreted with the aid of theoretical studies carried out within the BCS-based QRP…
High-Kfour-quasiparticle states inGd138
2011
States above the known ${K}^{\ensuremath{\pi}}={8}^{\ensuremath{-}}$ 6 $\ensuremath{\mu}$s isomer in $^{138}\mathrm{Gd}$ have been populated with the $^{106}\mathrm{Cd}$($^{36}\mathrm{Ar}$,$2p2n$) reaction at a beam energy of 180 MeV at the University of Jyv\"askyl\"a, Finland. The recoil-isomer tagging technique was utilized to correlate delayed $\ensuremath{\gamma}$-ray decays, detected in the GREAT focal plane spectrometer, with prompt decays measured in the JUROGAM II spectrometer at the target position. The lifetime of the ${K}^{\ensuremath{\pi}}={8}^{\ensuremath{-}}$ isomeric state has been remeasured as 6.2(2) $\ensuremath{\mu}$s. Two high-lying strongly coupled bands have been estab…
Interplay of quasiparticle and phonon excitations in 181Hf observed through (n,γ) and reactions
2002
Abstract Nuclear levels of 181 Hf were investigated in the range up to 3 MeV excitation energy by (n, γ ) and (d,p) reactions. Over 170 levels and about 390 γ -transitions were established most of them for the first time. 25 rotational bands were identified. Comparison of the results of the two reactions yields information on the fine structure in the fragmentation of Nilsson strength. The states below 2 MeV with the most complete spectroscopic information were interpreted in terms of the Quasiparticle Phonon Model (QPM). Excitation energies, electromagnetic transition rates, γ -branchings and spectroscopic factors are discussed in connection with their possible structure.
Low-spin mixed particle–hole structures in 185W
2005
Abstract The level structure of 185W has been studied using the prompt and delayed gamma–gamma coincidences from thermal neutron capture in 184W accompanied with the one-nucleon transfer reactions ( d , p ) and ( d , t ) with polarized beams. From these data and those of previous studies a total of 183 levels has been established for energies below 3 MeV. Many of these states have been grouped into rotational bands built on 28 intrinsic states of quasiparticle and quasiparticle-plus-phonon character. Although the DWBA analysis permitted definite spin–parity assignments for most of states a large number of particle transitions have ‘anomalous’ angular and asymmetry shapes with respect to the…
Search for a 2-quasiparticle high-Kisomer inRf256
2011
The energies of 2-quasiparticle (2-qp) states in heavy shell-stabilized nuclei provide information on the single-particle states that are responsible for the stability of superheavy nuclei. We have calculated the energies of 2-qp states in {sup 256}Rf, which suggest that a long-lived, low-energy 8{sup -} isomer should exist. A search was conducted for this isomer through a calorimetric conversion electron signal, sandwiched in time between implantation of a {sup 256}Rf nucleus and its fission decay, all within the same pixel of a double-sided Si strip detector. A 17(5)-{mu}s isomer was identified. However, its low population, {approx}5(2)% that of the ground state instead of the expected {a…
Muon-capture strength functions in intermediate nuclei of 0νββ decays
2019
Capture rates of ordinary muon capture (OMC) to the intermediate nuclei of neutrinoless double beta ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) decays of current experimental interest are computed. The corresponding OMC (capture-rate) strength functions have been analyzed in terms of multipole decompositions. The computed low-energy OMC-rate distribution to $^{76}\mathrm{As}$ is compared with the available data of Zinatulina et al. [Phys. Rev. C 99, 024327 (2019)]. The present OMC computations are performed using the Morita-Fujii formalism by extending the original formalism beyond the leading order. The participant nuclear wave functions are obtained in extended no-core singl…
Anomalous Fluctuations of Nematic Order in Solutions of Semiflexible Polymers
2016
The nematic ordering in semiflexible polymers with contour length $L$ exceeding their persistence length $\ell_p$ is described by a confinement of the polymers in a cylinder of radius $r_{eff}$ much larger than the radius $r_\rho$, expected from the respective concentration of the solution. Large scale Molecular Dynamics simulations combined with Density Functional Theory are used to locate the Isotropic-Nematic ($I-N$)-transition and to validate this cylindrical confinement. Anomalous fluctuations, due to chain deflections from neighboring chains in the nematic phase are proposed. Considering deflections as collective excitations in the nematically ordered phase of semiflexible polymers el…
The Topological Phase Transitions Related to Fermion Condensate
2014
In this chapter, we consider so-called topological phase transitions, taking place in normal Fermi liquid. In other words, here we are dealing with different instabilities of normal Fermi liquids relative to several kinds of perturbations of initial quasiparticle spectrum \(\varepsilon (p)\) and occupation numbers \(n(p)\) associated with the emergence of a multi-connected Fermi surface. Depending on the parameters and analytical properties of the Landau interaction, such instabilities lead to several possible types of restructuring of initial Landau Fermi liquid ground state. This restructuring generates topologically distinct phases. One of them is the FC discussed above, another one belo…
Effect of a Triaxial Nuclear Shape on Proton Tunneling: The Decay and Structure of 145Tm
2007
Gamma rays deexciting states in the proton emitter 145Tm were observed using the recoil-decay tagging method. The 145Tm ground-state rotational band was found to exhibit the properties expected for an h{11/2} proton decoupled band. In addition, coincidences between protons feeding the 2{+} state in 144Er and the 2{+}-->0{+} gamma-ray transition were detected, the first measurement of this kind, leading to a more precise value for the 2{+} excitation energy of 329(1) keV. Calculations with the particle-rotor model and the core quasiparticle coupling model indicate that the properties of the pi{11/2} band and the proton-decay rates in 145Tm are consistent with the presence of triaxiality with…