Search results for "SIP"
showing 10 items of 1280 documents
Effects of orbital occupation on 0νββ nuclear matrix element
2009
We have used the recently measured neutron occupancies in the 76 Ge and 76 Se nuclei as a guideline to define the neutron quasiparticle states in the 1p0f0g shell. The adjacent odd-mass nuclei help define the corresponding proton quasiparticle states. We insert the obtained quasiparticles in a proton-neutron quasiparticle random-phase approximation (pnQRPA) calculation of the nuclear matrix element of the neutrinoless double beta (0 νββ ) decay of 76 Ge. It is found that the resulting value of the 0 νββ matrix element is not far from the recently reported shell-model result.
High-spin states beyond the proton drip-line: Quasiparticle alignments in 113 Cs
2014
Abstract Excited states have been studied in the deformed proton emitter 113Cs. Gamma-ray transitions have been unambiguously assigned to 113Cs by correlation with its characteristic proton decay, using the method of recoil-decay tagging. Two previously identified rotational bands have been observed and extended to tentative spins of 45/2 and 51 / 2 ħ , with excitation energies over 8 MeV above the lowest state. These are the highest angular momenta and excitation energies observed to date in any nucleus beyond the proton drip-line. Transitions in the bands have been rearranged compared to previous work. A study of aligned angular momenta, in comparison to the predictions of Woods–Saxon cra…
Quantum bubble dynamics in the presence of gravity
1991
Abstract The dynamics of spherical quantum bubbles in 3+1 dimensions is governed by a Klein-Gordon-type equation which simulates the quantum mechanical motion of a relativistic point particle in 1+1 dimensions. This dimensional reduction is especially clear in the minisuperspace formulation first used in quantum cosmology and adapted here to quantum bubble dynamics. The payoff of this formulation is the discovery of the gravitational analogue of the Klein effect, namely the crossing of positive and negative energy levels of the particle spectrum induced by an external gravitational field. This phenomenon gives rise to a finite probability that a vacuum bubble might tunnel from an initial bo…
Effects of weakly coupled channels on quasielastic barrier distributions
2009
Heavy-ion collisions often produce fusion barrier distributions with structures displaying a fingerprint of couplings to highly collective excitations. Similar distributions can be obtained from large-angle quasielastic scattering, although in this case, the role of the many weak direct-reaction channels is unclear. For $^{20}\mathrm{Ne}+^{90}\mathrm{Zr}$, we have observed the barrier structures expected for the highly deformed neon projectile; however, for $^{20}\mathrm{Ne}+^{92}\mathrm{Zr}$, we find significant extra absorption into a large number of noncollective inelastic channels. This leads to smearing of the barrier distribution and a consequent reduction in the ``resolving power'' o…
α-decay spectroscopy of deformed nuclei reexamined
2008
We perform an extensive analysis of $\ensuremath{\alpha}$-decays to ${2}^{+}$ and ${4}^{+}$ states in deformed even-even nuclei by using the stationary coupled channels approach. Collective excitations are described within the rigid rotor model. The $\ensuremath{\alpha}$-nucleus interaction is given by a double folding procedure with M3Y plus Coulomb nucleon-nucleon forces. We use a repulsive potential with one independent parameter in order to localize the $\ensuremath{\alpha}$-particle on the nuclear surface and to fit the experimental $Q$-value. The decaying state is identified with the first resonance inside the resulting pocket-like potential, as suggested by microscopic calculations. …
Identification of theKπ=8−rotational band in138Gd
1998
A ${K}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ collective rotational band has been established upon the 6 $\ensuremath{\mu}$s isomeric state in the very neutron-deficient nucleus ${}^{138}\mathrm{Gd}.$ The band was observed using a technique involving the correlation of $\ensuremath{\gamma}$-ray transitions across the isomeric state. The single-particle configuration of the isomer has been deduced from the $\ensuremath{\Delta}I=2$ to $\ensuremath{\Delta}I=1$ intensity branching ratios. In addition, a series of other $\ensuremath{\gamma}$-ray transitions were observed which are reasoned to be part of a higher-lying four quasiparticle structure which decays through the ${K}^{\ensuremath{\pi}…
Relations between the Hepp-Lieb and the Alli-Sewell Laser Models
2009
In this paper we show that the dissipative version of the laser model proposed by Alli and Sewell can be obtained by considering the stochastic limit of the (open system) hamiltonian introduced by Hepp and Lieb in their seminal work. We also prove that the Dicke-Haken-Lax hamiltonian produces, after the stochastic limit is considered, the generator of a semigroup with equations of motion very similar to those of Alli-Sewell, and coinciding with these under suitable conditions.
Pronounced shape change induced by quasiparticle alignment
2000
Mean lifetimes of high-spin states of Kr-74 have been determined using the Doppler-shift attenuation method. The high-spin states were studied using the Ca-40(Ca-40, alpha 2p) reaction at a beam energy of 160 MeV with the GASP gamma-ray spectrometer. The ground-state band and negative parity side band show the presence of three different configurations in terms of transitional quadrupole deformations. A dramatic shape change was found along the ground-state band after the S-band crossing. The deduced quadrupole deformation changes are well reproduced by cranked Woods-Saxon Strutinsky calculations.
Experimental evidence for chirality in the odd-A 105Rh
2004
Abstract High-spin states in 105 Rh were populated by the 96 Zr( 13 C, p3n) reaction at beam energies of 51 and 58 MeV, and studied using the EUROBALL IV γ -ray spectrometer and the DIAMANT charged particle array. A pair of nearly degenerate Δ I = 1 three-quasiparticle bands with the same spins and parity have been observed. Comparison of the experimental results with tilted axis cranking calculations confirms the chiral character of the two bands, while arguments based on the excitation of particles within the π g 9 / 2 ν ( h 11 / 2 ) 2 configuration of the yrast band and comparison with the previously observed γ band exclude the other possible interpretations. This is the first experiment…
Strength ofJπ=1+Gamow-Teller and isovector spin monopole transitions in double-β-decay triplets
2014
In this work we study systematically the energetics and intensity distributions of Gamow-Teller (GT${}^{\ifmmode\pm\else\textpm\fi{}}$) and isovector spin monopole (IVSM${}^{\ifmmode\pm\else\textpm\fi{}}$) transitions from the ground states of the pairs ($^{76}\mathrm{Ge}$,$^{76}\mathrm{Se}$), ($^{82}\mathrm{Se}$,$^{82}\mathrm{Kr}$), ($^{100}\mathrm{Mo}$,$^{100}\mathrm{Ru}$), ($^{116}\mathrm{Cd}$,$^{116}\mathrm{Sn}$), ($^{128}\mathrm{Te}$,$^{128}\mathrm{Xe}$), ($^{130}\mathrm{Te}$,$^{130}\mathrm{Xe}$), and ($^{136}\mathrm{Xe}$,$^{136}\mathrm{Ba}$), of double-beta-decay initial and final nuclei, to the ${J}^{\ensuremath{\pi}}={1}^{+}$ excited states of the intermediate odd-odd nuclei $^{76}\…