Search results for "semiclassical"
showing 10 items of 111 documents
Shears mechanism in109Cd
2000
Lifetimes of high-spin states in two $\ensuremath{\Delta}I=1$ bands and one $\ensuremath{\Delta}I=2$ band in ${}^{109}\mathrm{Cd}$ have been measured using the Doppler shift attenuation method in an experiment performed using the ${}^{96}\mathrm{Zr}{(}^{18}\mathrm{O},5n)$ reaction with the GAMMASPHERE array. Experimental total angular momenta and reduced transition strengths for both $\ensuremath{\Delta}I=1$ bands were compared with tilted axis cranking (shears mechanism) predictions and the $\ensuremath{\Delta}I=2$ band with principal axis cranking predictions, based on configurations involving two proton ${g}_{9/2}$ holes and one or three valence quasineutrons from the ${h}_{11/2}$ and mi…
High temperature giant dipole and isoscalar resonances
1990
We present a systematic study of the Giant Dipole Resonance (GDR) at high temperatures (T≧4 MeV) in the framework of a semiclassical approximation that uses them1 andm3 RPA sum rules to estimate the GDR mean energy. We focus on the evolution withT of the collective nature of the GDR and of theL=0, 2, 3 and 4 isoscalar resonances. We find that the GDR remains particularly collective at highT, suggesting that it might be possible to observe it experimentally even at temperatures close to the maximum one a nucleus can sustain.
Description of sub-barrier heavy ion fusion in a semiclassical quantum tunneling model
1996
In this paper we apply the semiclassical method based on the Feynman path integral formalism to sub-barrier fusion of heavy nuclei. Cross sections are calculated and compared to experimental data and to coupled-channel calculations for different mass systems: 32S124Mg, 58Ni164Ni, and 16O1208Pb. The semiclassical method and coupled-channel calculations give comparable results. It is found that the coupling produces a renormalization of the barrier that is responsible for the enhancement of sub-barrier fusion cross sections and a dissipative force along the classical tunneling path.
Collective subspaces for large amplitude motion and the generator coordinate method
1979
The collection path $|\ensuremath{\varphi}(q)〉$ to be used in a microscopic description of large amplitude collective motion is determined by means of the generator coordinate method. By varying the total energy with respect to $|\ensuremath{\varphi}(q)〉$ and performing an adiabatic expansion a hierarchy of equations is obtained which determines uniquely a hierarchy of collective paths with increasing complexity. To zeroth order the $|\ensuremath{\varphi}(q)〉$ are Slater determinants, to first order they include 2p-2h correlations. In both cases simple noninterative prescriptions for an explicit construction of the path are derived. For a correlated path their solutions agree at the Hartree…
Comparing non-perturbative models of the breakup of neutron-halo nuclei
2012
Breakup reactions of loosely-bound nuclei are often used to extract structure and/or astrophysical information. Here we compare three non-perturbative reaction theories often used when analyzing breakup experiments, namely the continuum discretized coupled channel model, the time-dependent approach relying on a semiclassical approximation, and the dynamical eikonal approximation. Our test case consists of the breakup of 15C on Pb at 68 MeV/nucleon and 20 MeV/nucleon.
SEMICLASSICAL DESCRIPTION OF SPIN EXCITATIONS OF THE PARTICLE-CORE INTERACTION SYSTEM
1993
A model Hamiltonian describing a nucleon moving in a shifted oscillator well and inter-acting with a harmonic core through a quadrupole-quadrupole term is semiclassically treated. The solutions of the linearised equations of motion are quantised by the Bohr-Sommerfeld procedure. Among the four RPA modes, there is one which corresponds to the harmonic vibration of the spin degree of freedom. This mode is analogous to the spin wave mode describing a system of interacting spins placed in a magnetic field. The state describes a harmonic wobbling motion around a stationary state belonging to the ground rotational band.
A field theoretic realization of a universal bundle for gravity
1992
Abstract Based upon a local vector supersymmetry algebra, we discuss the general structure of the quantum action for topological gravity theories in arbitrary dimensions. The precise form of the action depends on the particular dimension, and also on the moduli space of interest. We describe the general features by examining a theory of topological gravity in two dimensions, with a moduli space specified by vanishing curvature two-form. It is shown that these topological gravity models together with their observables provide a field theoretic realization of a universal bundle for gravity.
First identification of rotational band structures inRe9175166
2015
Despite that it is more than 100 years since the atomic nucleus was first dis- covered by Ernest Rutherford and coworkers, many of its features still elude our understanding. The fact that the fundamental interactions between the nuclear constituents; nucleons, and ultimately quarks, are not yet known in detail, and the complexity of the nuclear many-body system compound the great challenges facing theoretical interpretations of experimental data. It is therefore important to focus on distinct phenomena where experimental mea- surements can be compared with theoretical predictions, providing stringent tests of theory. One such area is the nuclear phenomenology of collective excitations rela…
Neutron removal in peripheral relativistic heavy-ion collisions
1995
We investigate the relativistic Coulomb fragmentation of $^{197}\mathrm{Au}$ by heavy ions, leading to one-, two-, and three-neutron removal. To resolve the ambiguity connected with the choice of a specific minimum impact parameter in a semiclassical calculation, a microscopic approach is developed based on nucleon-nucleon collisions (``soft-spheres'' model). This approach is compared with experimental data for $^{197}\mathrm{Au}$ at 1 GeV/nucleon and with a calculation using the ``sharp-cutoff'' approximation. We find that the harmonic-oscillator model predicting a Poisson distribution of the excitation probabilities of multiphonon states gives a good agreement with one-neutron removal cro…
Excitation and ionization of Rydberg atoms by short half-cycle pulses
1999
Simple semiclassical formulas are derived for the probability of excitation and ionization of Rydberg atoms irradiated by a half-cycle pulse whose duration is shorter than the Kepler period. The calculated ionization probabilities are in good agreement with the experimental data of Jones, You, and Bucksbaum [Phys. Rev. Lett. 70, 1236 (1993)] and with previous calculations.