LANZA , Edoardo G.

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.

The construction of differential cross sections as a function of excitation energy for systems with a collection of low- and high-lying intrinsic vibrational modes has been attempted in the past. A prescription is proposed here that simplifies the implementation of such calculation schemes with a remarkable reduction in computational time.

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...

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...

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...

We calculate the inelastic scattering cross sections to populate one- and two-phonon states in heavy ion collisions with both Coulomb and nuclear excitations. Starting from a microscopic approach based on random-phase approximation, we go beyond it in order to treat anharmonicities and nonlinear terms in the ...

We perform microscopic calculations of the inelastic cross sections for the double and triple excitation of giant resonances induced by heavy-ion probes within a semiclassical coupled-channels formalism. The channels are defined as eigenstates of a bosonic quartic Hamiltonian constructed in terms of collective random-phase approximation...

We show that the non-linearities of large amplitude motions in atomic nuclei induce giant quadrupole and monopole vibrations. As a consequence, the main source of anharmonicity is the coupling with configurations including one of these two giant resonances on top of any state. Two-phonon energies are often lowered by one or two MeV because of...

The coupling of the high-lying dipole mode to the low-lying quadrupole modes for the case of deformed γ-unstable nuclei is studied. Results from the geometrical model are compared to those obtained within the dipole boson model. Consistent results are obtained in both models.The dipole boson model is treated within the intrinsic frame, with...

The excitation of the Pygmy Dipole Resonance (PDR) in the 68Ni nucleus, above the neutron emission threshold, via an isoscalar probe has been observed for the first time. The excitation has been produced in reactions where a 68Ni beam, obtained by the fragmentation of a 70Zn primary beam at INFN-LNS, impinged on a 12C target. The γ-ray decay...