Generator Coordinate Method Calculation Research Articles

Generator coordinate method calculation of the E2 decay lifetime of shape isomers in the actinide region.

We apply the generator coordinate method in a fully microscopic calculation of the {ital E}2 decay lifetime of the shape isomeric states of {sup 236}U, {sup 238}U, and {sup 240}Pu. The basis states have been generated by constrained Hartree-Fock Bardeen-Cooper-Schrieffer calculations with the SkM{sup {asterisk}} force. Triaxial quadrupole deformations have been included. Implications upon the decay lifetime of the quasidegeneracy of the isomeric state and the one-phonon excitation in the first well are examined. {copyright} {ital 1996 The American Physical Society.}

Generator coordinate method calculations for 4He and 16O nuclei.

Generator coordinate method calculations, including the case of two-generator coordinates, which is not usually considered in the relevant scientific literature, are performed for nuclear state energies, as well as momentum and density distributions of the [sup 4]He and [sup 16]O nuclei. The construction potential used behaves like an harmonic oscillator at large distances from the center of the potential but it has also a strong short-range repulsion, which is expected to simulate, to some extent, effects of the inclusion of short-range correlations in the harmonic oscillator many-body wave function. The results are compared with available experimental information and discussed.

Generator coordinate calculations for breathing-mode giant monopole resonance in the relativistic mean-field theory.

The breathing-mode giant monopole resonance (GMR) is studied within the framework of the relativistic mean-field theory (RMF) using the generator coordinate method (GCM). The constrained incompressibility and the excitation energy of isoscalar giant monopole states are obtained for finite nuclei with various sets of Lagrangian parameters. A comparison is made with the results of nonrelativistic constrained Skyrme Hartree-Fock (HF) calculations and with those from Skyrme random phase approximation (RPA) calculations. In the RMF theory the GCM calculations give a transition density for the breathing mode, which greatly resembles that obtained from the Skyrme HF+RPA approach and also that from the scaling mode of the GMA. From the systematic study of the breathing-mode as a function of the incompressibility in GCM, it is shown that the GCM succeeds in describing the GMR energies in nuclei and that the empirical breathing-mode energies of heavy nuclei can be reproduced by forces with an incompressibility close to K=300 MeV in the RMF theory.

GCM calculation of the E2 decay lifetimes of shape isomers

We apply the generator coordinate method (GCM) in a fully microscopic calculation of the E2 decay lifetime of the isomeric states of 238U, 230Thand 232Th. The basis states have been generated by constrained HFBCS calculations with the potential SkM∗. Triaxial quadrupole deformations have been included. Comparison is made with experiment in the case of 238U and experimenters are urged to search for the predicted decays in the thorium isotopes.

Alpha + alpha scattering in a microscopic model with monopolar distortion.

The feasibility of general generator coordinate method calculations with monopolar specific distortion is investigated on \ensuremath{\alpha}+\ensuremath{\alpha} scattering. A triple integral transform of matrix elements calculated with Slater determinants eliminates spurious center-of-mass components and uniformizes the basis functions of the relative motion. Besides the \ensuremath{\alpha}-particle ground state, the ${\mathrm{\ensuremath{\alpha}}}^{\mathrm{*}}$ breathing mode and two pseudostates are included in the calculation. Collision matrices are determined up to 400 MeV with the microscopic R-matrix method. Different types of resonances and the \ensuremath{\alpha}+${\mathrm{\ensuremath{\alpha}}}^{\mathrm{*}}$ inelastic cross section are discussed. The nature of Pauli resonances, i.e., resonances related to almost forbidden states and their relation with the Levinson theorem are investigated in a single-channel approximation.

Quadrupole collective correlations and the depopulation of the superdeformed bands in mercury

Fully self-consistent generator coordinate method calculations have been performed on a basis of quadrupole constrained Hartree-Fock plus BCS wave functions for the five even mercury isotopes 190–198Hg. The gcm results support conclusions drawn from previous HF + BCS calculations. The predicted evolution of superdeformed band head (shape isomer) properties as a function of the neutron number is consistent with the data. Using calculated transition matrix elements, we evaluate in-band versus out-of-band quadrupole decay and explain the sudden termination of the super-deformed band.

On the normal modes of vibration in light deformed nuclei

An analysis of generator coordinate method calculations on density vibrations in axially deformed light nuclei, demonstrates that the normal modes are harmonic vibrations parallel and orthogonal to the symmetry axis.