ANDRÉS MARTÍN , María Victoria

We present a short review of the properties of the so-called Pygmy Dipole Resonance (PDR) which can be studied with both isovector and isoscalar probes. This is possible due to the particular property of this new mode where the isoscalar and isovector characters are mixed. The use of both probes unveils new features which otherwise will...

It is shown that the use of a proper form factor in the study of the pygmy dipole resonance (PDR) is of paramount importance in order to determine the correct values for the relevant quantities characterizing these new modes. Form factors calculated within a microscopic model are compared with those provided by different macroscopic collective...

Within the Feshbach formalism we calculate the nucleus-nucleus dynamical polarization potential arising from the coupling of the elastic channel to the collective vibrational states, described by the random-phase approximation. Calculations for the systems O16+40Ca and Ca40+40Ca show the importance of the high-lying states. They give the main...

This is a reply to the preceding Comment. We confirm the results of our paper. The differences between our calculations and those of the preceding Comment come mainly from the form factors. Our random-phase-approximation-based form factors are in good agreement with those obtained by using experimental transition densities.

A simple model to understand the reaction mechanisms in the fusion of polarized heavy ions based on tidal symmetry, the sudden approximation and barrier penetration is presented. The model is applied to 23Na+208Pb. The effect of the ground state reorientation and the coupling to rotational states is studied. Enhancement of the sub-barrier...

A dynamical polarization potential is defined taking into account the effects on the elastic channel due to the excitation of vibrational collective modes, described within the random-phase approximation. The probability amplitudes for exciting these modes are evaluated by integration along classical trajectories determined by the real part of...

Pygmy dipole resonance can be populated via isoscalar probes due to the strong mixing of isoscalar and isovector components. The physical quantities are usually extracted by the use of reaction theory calculations. There, the most important ingredient is the form factor which contains all the relevant properties of the states we are dealing...

The effect of a quadrupole force on a set of degenerate states of a rotational band with arbitrary spin projection along the symmetry axis K is studied. Analytic expressions for the eigenvalues and eigenvectors are obtained in terms of a set of orthogonal polynomials. This is applied to the collision of a spherical nucleus with a deformed one...

From a compound nucleus level-density-dependent imaginary potential an energy-and angular-momentum-dependent polarization potential is obtained by using the dispersion relation. The effect of coupling in this way the compound nucleus states to the elastic channel is to introduce a strongly attractive real polarization potential at small...

Two-dimensional quantum square wells and rectangular billiards with commensurate sides are simple systems which exhibit accidental degeneracies. We show that a recent analysis for square wells can be similarly applied to rectangular wells with commensurate sides

The two-dimensional square-well potential is one of the simplest quantum-mechanical systems that exhibits accidental degeneracy. We show that the double degeneracy present is a consequence of a dynamical symmetry and derive a new symmetry group associated with the system

We apply boson expansion methods to an extended exactly solvable Lipkin-Meshkov-Glick model including anharmonicities in analogy with previous microscopic calculations. We study the effects of different approximations present in these calculations, among which the truncation of the Hamiltonian and of the space, in connection with the study of...

We study, within a semiclassical coupled-channels approach, the possible effects of anharmonicities and non linearities on the excitation of the so-called pygmy resonances in several Sn isotopes and using two different Skyrme interactions. In the energy region of the pygmy resonances, there are a few low-lying multiphonon states. The question...

The nature of the low-lying dipole states in neutron-rich nuclei, often associated to the Pygmy Dipole Resonance, has been investigated. This has been done by describing them within the Hartree-Fock plus RPA formalism. The analysis shows that they are not of collective nature although many particle-hole configurations participate to their...

We study heavy-ion inelastic scattering processes in neutron-rich nuclei including the full response to the different multipolarities. Among these we focus in particular on the excitation of low-lying dipole states commonly associated to the pygmy dipole resonance. The multipole response is described within the Hartree-Fock plus RPA formalism...

An imaginary potential associated with the inelastic excitation of the nuclei is computed in a multiphonon excitation model based on the random phase approximation. The surface properties of this potential are found to be dominated by giant-resonance degrees of freedom.

We study the pygmy resonances in Sn isotopes within a microscopic multiphonon approach which has been successfully applied to heavy ion reactions in recent years. In the energy region of the pygmy resonances there are a few low lying multiphonon states. The question is whether they may contribute to the observed peak. Calculations show that the...

The effect of deformation on the excitation of multiple giant dipole resonances is studied. Analytical expressions are derived in the framework of the interacting boson model for the energies and E1 properties of giant dipole resonances in spherical and deformed nuclei, and a numerical treatment of transitional nuclei is proposed....

We present an extension of the random-phase approximation (RPA) where the RPA phonons are used as building blocks to construct the excited states. In our model, that we call double RPA (DRPA), we include up to two RPA phonons. This is an approximate and simplified way, with respect to the full second random-phase approximation (SRPA), to extend...