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The pairing correlations of the nucleus 120Sn are calculated by solving the Nambu–Gor’kov equations, including medium polarization effects resulting from the interweaving of quasiparticles, spin and density vibrations, taking into account, within the framework of nuclear field theory (NFT), processes leading to self-energy and vertex corrections and to the induced pairing interaction. From these r
The modern theory of the atomic nucleus results from the merging of the liquid drop model of Niels Bohr and Fritz Kalckar, and of the shell model of Marie Goeppert Meyer and Hans Jensen. The first model contributed the concepts of collective excitations. The second, those of independent-particle motion. The unification of these apparently contradictory views in terms of the particle-vibration and
A complete characterization of the structure of nuclei can be obtained by combining information arising from inelastic scattering, Coulomb excitation, and γ-decay, together with one- and two-particle transfer reactions. In this way it is possible to probe both the single-particle and collective components of the nuclear many-body wave function resulting from the coupling of these modes and, as a r
The (J, T)=(1, 1) parity doublet in 20Ne at 11.26 MeV is a good candidate to study parity violation in nuclei. However, its energy splitting is known with insufficient accuracy for quantitative estimates of parity violating effects. To improve on this unsatisfactory situation, nuclear resonance fluorescence experiments using linearly and circularly polarized γ-ray beams were used to determine the
Nuclear Field Theory of structure and reactions is confronted with observations made on neutron halo dripline nuclei, resulting in the prediction of a novel (symbiotic) mode of nuclear excitation, and on the observation of the virtual effect of the halo phenomenon in the apparently non-halo nucleus 7Li. This effect is forced to become real by intervening the virtual process with an external (t,p)
Intermediate mass stars develop a degenerate core constituted of O, Ne and Mg during their evolution. As the density in the core increases electron capture sets in igniting Ne and O burning. Particularly important is electron capture on 20Ne that has been found recently to be dominated by a second forbidden transition from the 0+ ground state of 20Ne to the 2+ ground state of 20F. We have performe
Recent data resulting from studies of two-nucleon transfer reaction on 11Li, analyzed through a unified nuclear-structure-direct-reaction theory have provided strong direct as well as indirect confirmation, through the population of the first excited state of 9Li and of the observation of a strongly quenched ground state transition, of the prediction that phonon-mediated pairing interaction is the
The effects of core polarization on the structure of Li and Be halos and their consequences on one-and two-neutron transfer reactions are discussed.
Soon after the formulation of BCS theory [1], it was recognized by Bohr, Mottelson, and Pines that the existence of an energy gap in the intrinsic excitation spectrum of deformed nuclei displayed a suggestive analogy with that observed in the electronic spectra of metallic superconductors and could, like this one, be described at profit in terms of correlated pairs [2]. Their paper represented the
We review recent progress made in understanding the role of medium polarization on superuidity in finite nuclei and in the inner crust of neutron stars. The interweaving of collective and quasiparticle degrees of freedom is treated within the framework of Nuclear Field Theory, propagating the basic renormalization processes through the Nambu-Gor’kov equations. It is then possible to obtain quantit
In this short letter we briefly address two important points of two-neutron transfer reactions, namely the successive nature of the process and the role of pairing correlations during this sequential transfer. The discussion is made within the 2-step DWBA formalism. The calculations were carried out making use of software specifically developed for this purpose, which includes successive, simultan
Pairing rotations and pairing vibrations are collective modes associated with a field, the pair field, which changes the number of particles by two. Consequently, they can be studied at profit with the help of two-particle transfer reactions in superfluid and in normal nuclei, respectively. The advent of exotic beams has opened, for the first time, the possibility to carry out such studies in medi
Absolute values of two-particle transfer cross sections along the Sn-isotopic chain are calculated. They agree with measurements within errors and without free parameters. Within this scenario, the predictions concerning the absolute value of the two-particle transfer cross sections associated with the excitation of the pairing vibrational spectrum expected around the recently discovered closed sh
The properties of a cylindrical 1" × 1" and 3" × 3" LaBr3:Ce scintillators (Brillance 380) have been investigated. The first crystal has been analyzed in terms of its self activity due to unstable contaminants emitting a and β particles eventually followed by γ-rays. Coincidence measurements between LaBr3:Ce signals and γ-rays in a HPGe detector were made. The second crystal has been irradiated wi
Within the framework of nuclear field theory (NFT), the spectrum of atomic nuclei is described in terms of collective and quasiparticle degrees of freedom, that is, of elementary modes of excitation that are directly related to experiment and of their coupling, whose strength and form factors are the basic ingredients entering in the calculations of absolute cross sections of inelastic and of one-
We discuss the solution of the Dyson equation (also known as the Nambu-Gor'kov equation) for the case of medium polarization Nuclear Field Theory (NFT) processes in nuclei, and apply it to the nucleus 120Sn. Starting from a mean field obtained with the Sly4 effective nucleon-nucleon force, (mk = 0.7), we renormalize the single-particle states and the pairing interaction through the coupling to col
We present a brief introduction to the second order DWBA reaction formalism which we have used to perform the theoretical analysis of two-nucleon transfer reactions induced both by heavy and light ions. We also show an example of such a calculation, emphasizing the connection between the structure aspects of the problem and the resulting predicted two-neutron transfer cross section. The calculatio
We solve the Nambu-Gor'kov equations in 120Sn, demonstrating that the coupling of quasiparticles with collective surface vibrations renormalizes the low-lying part of the nuclear spectrum and influences pairing correlations in a substantial way.
The six measured ASn(p,t)A-2Sn(gs) transfer absolute differential cross sections (A = 112, 116, 118, 120, 122, and 124) are calculated within the framework of DWBA taking into account successive, simultaneous and non-orthogonality contributions, and making use of BCS spectroscopic amplitudes which reproduce the overall distortion of the Fermi distribution around εF . Theory provides an overall acc
High polarizability and halo phenomena are strongly correlated, as evidenced by the qualitative changes of the nuclear spectrum which arise taking into account the dynamical coupling of the valence neutrons with the collective vibrations of the system. Direct experimental evidence of their role in the induced pairing interaction binding the halo neutrons of 11Li to the core 9Li is provided by the
