Search results for "Phonon"
showing 10 items of 466 documents
Shell model and octupole states in148Gd from in-beam experiments
1990
Through (α, 4n) and (τ, 3n) reactions the high-spin states in the two-neutron nucleus148Gd were populated up toI π=21− at 7.2 MeV, including numerous states above the yrast line. The148Gd energy spectrum is interpreted in terms of the spherical shell model. Identification of the (νf 7/2 i 1 3/2)10− state gives the νi 13/2 single particle energy free of octupole admixtures as 2.1(1) MeV. Eight high-spin states between 1.2 and 3.7 MeV were identified as the couplings of the two valence-particles to the146Gd octupole phonon, and three above-lying levels are assigned as double-octupole excitations including a 12+ state which decays by anE3-E3 stretched cascade. All these octupole levels can be …
Electron–phonon interaction in a thin Al–Mn film
2006
Abstract Aluminum doped with manganese is an interesting novel material with applications in normal metal–insulator–superconductor (NIS) tunnel junction devices and transition-edge sensors at sub-Kelvin temperatures. We have studied the electron–phonon (e–p) coupling in a thin aluminum film doped with 1% manganese, with a measuring technique based on DC hot-electron effect. The electron temperature was measured with the help of symmetric normal metal–insulator–superconductor tunnel-junction pairs (SINIS-thermometers). Measurements show that the temperature dependence of the e–p interaction is not consistent with existing theories for disordered metals, but follows a higher power law.
Low-lying collective states inRu98–106isotopes studied using a microscopic anharmonic vibrator approach
2003
Anharmonic features of the low-lying collective states in the $^{98--106}\mathrm{Ru}$ isotopes have been investigated systematically by using the microscopic anharmonic vibrator approach (MAVA). MAVA is based on a realistic microscopic $G$-matrix Hamiltonian, only slightly renormalized in the adopted large realistic single-particle spaces. This Hamiltonian is used to derive equations of motion for the mixing of one- and two-phonon degrees of freedom starting from collective phonons of the quasiparticle random-phase approximation. Analysis of the level energies and the electric quadrupole decays of the two-phonon type of states indicates that $^{100}\mathrm{Ru}$ can be interpreted as being a…
Electromagnetic excitation of the two-phonon giant dipole resonance
1994
Abstract The nuclear response of 136 Xe and 208 Pb to electromagnetic excitation was studied in peripheral, near-relativistic heavy-ion collisions. Large cross sections were observed for the one-phonon and two-phonon isovector giant dipole resonance. The results, in particular the unexpectedly large strength found for the double giant dipole resonance, are discussed and compared to that of other recent measurements.
Microscopic quasiparticle-phonon description of odd-mass127−133Xeisotopes and their β decay
1998
Quasiparticle-phonon equations of motion are solved starting from a microscopic realistic many-body Hamiltonian. In this microscopic quasiparticle-phonon model (MQPM) the relevant part of the three-quasiparticle Hilbert space may possibly be taken into account even in calculations using large single-particle bases. As an example, the MQPM is applied to the calculation of energy levels and Fermi and Gamow-Teller beta-decay transition amplitudes for transitions between odd-mass ${}^{127\ensuremath{-}133}\mathrm{Xe}$, ${}^{127\ensuremath{-}133}\mathrm{I}$, and ${}^{127\ensuremath{-}133}\mathrm{Cs}$ isotopes. Considering the fully microscopic nature of the MQPM, comparison of its results and da…
Optimizing the operating temperature of a transition edge sensor
2006
We discuss the theory for optimizing the operating temperature of a voltage biased superconducting transition edge sensor (TES) in terms of energy resolution and speed, considering only internal detector noise sources. The noise processes included in the modeling are the unavoidable Johnson and phonon noise. The phonon noise is calculated for the case of ballistic transport. If other external and excess internal noise sources are not dominant, an optimal operating temperature can be found to minimize the energy resolution. The detector slows down by approximately a factor of two at the optimal energy resolution point.
Neutrino-pair emission due to electron-phonon scattering in a neutron star crust: a reappraisal
2000
The process of $\nu \bar{\nu}$ radiation due to interaction of electrons with phonons in the crust of a cooling neutron star is studied with the consistent account of an electromagnetic coupling between electrons in the medium. The wavelength of radiated neutrinos and antineutrinos is typically much larger than the electron Debye screening distance in the medium, and therefore plasma polarization substantially modifies the effective weak current of the electron. Is shown, that under above conditions plasma polarization screens totally a vector weak interaction of the electron with a neutrino field. As a result, the $\nu \bar{\nu}$ emissivity is less in approximately 2.23 times than previous…
The response of (95,97)Mo to supernova neutrinos
2011
Knowledge about nuclear responses to neutrinos is essential for both astrophysical applications and studies of neutrino properties. We perform in this paper calculations of the cross sections for neutral-current neutrino scattering off the odd A = 95,97 Mo isotopes for energies appropriate for the detection of supernova neutrinos. Both the incoherent and coherent contributions to the cross sections are evaluated. The prominently contributing nuclear final states are identified and analysed. We employ the microscopic quasiparticle-phonon model (MQPM) to construct the wave functions of the initial and final nuclear states. The response of the aforementioned nuclei to supernova neutrinos are c…
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…