Search results for "Quasiparticle"
showing 10 items of 280 documents
Detailed study of the neutral-current neutrino–nucleus scattering off the stable Mo isotopes
2012
Abstract For neutrino detection and for various applications in astrophysics the knowledge of the nuclear responses to astrophysical neutrinos is crucial. Recent studies of neutrino interactions with the 100 Mo nucleus and the other stable molybdenum isotopes are important for the planned MOON (Mo Observatory of Neutrinos) detector. To this aim, in the present work we perform detailed nuclear structure calculations for the neutral-current neutrino–nucleus scattering off the stable molybdenum isotopes. We focus on the differential and total neutrino–nucleus cross sections as well as on flux averaged cross sections to various supernova neutrino spectra. We also propose a more efficient method…
Collective and broken pair states of65,67Ga
1999
Excited states of 65Ga and 67Ga nuclei were populated through the 12C(58Ni,αp) and 12C(58Ni,3p) reactions, respectively, and investigated by in-beam γ-ray spectroscopic methods. The NORDBALL array equipped with a charged particle ball and 11 neutron detectors was used to detect the evaporated particles and γ rays. The level schemes of 65,67Ga were constructed on the basis of γγ-coincidence relations up to 8.6 and 10 MeV excitation energy, and Iπ=27/2 and 33/2+ spin and parity, respectively. The structure of 65,67Ga nuclei was described in the interacting boson-fermion plus broken pair model, including quasiproton, quasiproton-two-quasineutron, and three-quasiproton fermion configurations in…
Microscopic anharmonic vibrator approach for beta decays
2007
Abstract We formulate a microscopic description of charge-changing excitations, including dynamical mixture of one- and two-phonon states. The present formalism generalizes our previous microscopic anharmonic vibrator approach (MAVA), designed to treat charge-conserving two- and four-quasiparticle degrees of freedom and their mixing. In the present formalism, the proton–neutron MAVA, pnMAVA, the main building blocks are the quasiparticle random-phase approximation (QRPA) phonons in the charge-conserving channels, and the proton–neutron QRPA (pnQRPA) phonons in the charge-changing channels. The QRPA and pnQRPA equations are directly used in deriving the equations of motion for two-phonon sta…
Isomer-tagged differential-plunger measurements in proton-unbound 144Ho
2010
The lifetime of an excited state above a weakly populated isomer in the proton-unbound odd-odd nucleus 144Ho has been measured using the recoil distance Doppler shift method. This measurement represents the first differential-plunger lifetime measurement to utilize recoil-isomer tagging. The first excited I[pi]=(10+) state above the two-quasiparticle [pi]h11/2[circle times operator][nu]h11/2(8+) isomer was determined to have a lifetime of [tau]=6(1)�ps. Potential energy surface calculations, based on the configuration-constrained blocking method, predict the isomeric state to have [gamma]-soft triaxial-nuclear shape with [gamma][approximate]24�. The lifetime of the (10+) state can be unders…
Identification of excited states in119Ba
2000
Excited states have been identified in the very neutron-deficient ${}^{119}\mathrm{Ba}$ nucleus. Two bands have been observed, which are likely to be based on ${h}_{11/2}$ and ${(g}_{7/2}{d}_{5/2})$ neutron orbitals. Despite this being the first observation of excited states in ${}^{119}\mathrm{Ba},$ the bands extend to $(75/2)\ensuremath{\Elzxh}$ and $(79/2)\ensuremath{\Elzxh},$ respectively. The bands have been assigned to ${}^{119}\mathrm{Ba}$ using gamma-recoil and gamma--x-ray coincidences. Several quasiparticle alignments have been identified, involving neutron ${(h}_{11/2}{)}^{2}$ and proton ${(h}_{11/2}{)}^{2}$ aligned configurations. Furthermore, the bands show features which are r…
Effects of orbital occupancies on the neutrinoless beta-beta matrix element of 76Ge
2008
In this work we use the recently measured neutron occupancies in the 76Ge and 76Se nuclei as a guideline to define the neutron quasiparticle states in the 1p0f0g shell. We define the proton quasiparticles by inspecting the odd-mass nuclei adjacent to 76Ge and 76Se. We insert the resulting quasiparticles in a proton-neutron quasiparticle random-phase approximation (pnQRPA) calculation of the nuclear matrix element of the neutrinoless double beta (0-nu-beta-beta) decay of 76Ge. A realistic model space and effective microscopic two-nucleon interactions are used. We include the nucleon-nucleon short-range correlations and other relevant corrections at the nucleon level. It is found that the res…
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…
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. …