Probing the shell valence structure underlying the B(E2: 0+->2+) for N,Z~40: preponderance of the p-n interaction over the sub-shell closures

The very simple product of the number of particles by the number of holes appearing in the expression of the reduced B(E2:0+->2+) transition probability of even-even nuclei obtained from the extension of the seniority scheme is used to analyze the experimental B(E2:0+->2+) values in the Cr up to Se isotopes. A new interpretation is given to the B(E2:0+->2+) measured in 68Ni and 70Zn. The B(E2:0+->2+) features of the even-even nuclei between Ni and Se with neutron number ranging from 28 up to 50 fit in with a global scenario involving p-n interaction. The evolution of the B(E2:0+->2+) curves presenting very large values is amazingly reproduced by very schematic binomial calculations.Comment: submitted to PRC the 14th May 2002, resubmitted to PRC the 24th June 200

Seniority scenario for the 68-72Zn and 66-68Ni B(E2)^ difference

The very simple product of the number of particles by the number of holes appearing in the expression of the reduced B(E2: 0+1 -> 2+1) (B(E2)^) transition probability of even-even nuclei obtained from the extension of the seniority scheme is used to analyze in a same time the experimental B(E2)^ values of 56-68 Ni and those of 62-72Zn. The evolution of these B(E2)^ values with neutron number fits in with a scenario involving p-n interaction

Excitations collectives à basse énergie : Etude microscopique de la rotation, de la vibration et de leur couplage dans les noyaux pair-pairs

We build microscopically a collective quadrupole Bohr hamiltonian in Hatree-Fock approximation. We seek a quantitative description of collective properties at low energy in medium and heavy nuclei. Dans ce qui suit, nous décrivons comme étant de "basse énergie" les régimes dynamiques dans lesquels le mouvement collectif est adiabatique par rapport aux modes associés aux degrés de liberté individuels. Dans la solution du problème nucléaire à N corps que nous proposons, nous avons fait les hypothèses suivantes : - Existence d'un champ moyen à tout instant (les corrélations d'appariement sont introduites de façon simplifiée au moyen d'une force de séniorité).- Existence de quelques variables collectives dont la variation temporelle contient toute la dynamique.- Adiabaticité du mouvement collectif. Ce travail constitue donc une formulation microscopique et une méthode de résolution praticable du Modèle Unifié de Bohr et Mottelson. Les spectres de basse énergie ainsi calculés pour quatre noyaux transitionnels (74Ge, 76Se, 110Cd, 186Pt) sont en excellent accord avec les données expérimentales.Dans ce travail, nous construisons le hamiltonien quadrupolaire collectif de Bohr le plus général, de façon purement microscopique au travers d'une approximation de l'approche adiabatique de Hartree-Fock dépendant du temps. L'objectif de ce travail est d'obtenir une description quantitative des propriétés collectives de basse énergie dans les noyaux moyens et lourds, au moyen d'une interaction effective à deux corps (type Skyrme). Dans ce qui suit, nous décrivons comme étant de "basse énergie" les régimes dynamiques dans lesquels le mouvement collectif est adiabatique par rapport aux modes associés aux degrés de liberté individuels.Dans la solution du problème nucléaire à N corps que nous proposons, nous avons fait les hypothèses suivantes :- Existence d'un champ moyen à tout instant (les corrélations d'appariement sont introduites de façon simplifiée au moyen d'une force de séniorité).- Existence de quelques variables collectives dont la variation temporelle contient toute la dynamique.- Adiabaticité du mouvement collectif.Ce travail constitue donc une formulation microscopique et une méthode de résolution praticable du Modèle Unifié de Bohr et Mottelson.Les spectres de basse énergie ainsi calculés pour quatre noyaux transitionnels (74Ge, 76Se, 110Cd, 186Pt) sont en excellent accord avec les données expérimentales

Quasiparticle random phase approximation predictions of the gamma-ray strength functions using the Gogny force

Dipole excitations of nuclei are crucial since they play an important role in nuclear reaction modeling in connection with the photoabsorption and the radiative capture processes. We present here results for the gamma-ray strength function obtained in large-scale axially-symmetric deformed quasiparticle (qp) random phase approximations approach using the finite-range Gogny force, with a particular emphasis on the E1 mode. The convergence with respect to the number of harmonic oscillator shells adopted and the cut-off introduced in the 2-quasiparticle excitation energy space is analyzed. The microscopic nature of our self-consistent Hartree-Fock-Bogoliubov plus QRPA (HFB+QRPA) calculation has unfortunately to be broken, some phenomenological corrections being needed to take into account effects beyond the standard 2-qp QRPA excitations and the coupling between the single-particle and low-lying collective phonon degrees of freedom. The corresponding phenomenological parameters are adjusted on experimental photoabsorption data. In such a procedure, a rather satisfactory description of experimental data is obtained. To study the sensitivity of these phenomenological corrections on the extrapolation, both at low energies and towards exotic neutron-rich nuclei, three different prescriptions are considered. They are shown to lead to rather similar predictions of the E1 strength at low energies as well as for exotic neutron-rich nuclei. The Gogny-HFB+QRPA strength is finally applied to the calculation of radiative neutron capture cross sections and the predictions compared with those obtained with more traditional Lorentzian-type approaches

Quasiparticle random phase approximation predictions of the gamma-ray strength functions using the Gogny force

International audienceDipole excitations of nuclei are crucial since they play an important role in nuclear reaction modeling in connection with the photoabsorption and the radiative capture processes. We present here results for the gamma-ray strength function obtained in large-scale axially-symmetric deformed quasiparticle (qp) random phase approximations approach using the finite-range Gogny force, with a particular emphasis on the E1 mode. The convergence with respect to the number of harmonic oscillator shells adopted and the cut-off introduced in the 2-quasiparticle excitation energy space is analyzed. The microscopic nature of our self-consistent Hartree-Fock-Bogoliubov plus QRPA (HFB+QRPA) calculation has unfortunately to be broken, some phenomenological corrections being needed to take into account effects beyond the standard 2-qp QRPA excitations and the coupling between the single-particle and low-lying collective phonon degrees of freedom. The corresponding phenomenological parameters are adjusted on experimental photoabsorption data. In such a procedure, a rather satisfactory description of experimental data is obtained. To study the sensitivity of these phenomenological corrections on the extrapolation, both at low energies and towards exotic neutron-rich nuclei, three different prescriptions are considered. They are shown to lead to rather similar predictions of the E1 strength at low energies as well as for exotic neutron-rich nuclei. The Gogny-HFB+QRPA strength is finally applied to the calculation of radiative neutron capture cross sections and the predictions compared with those obtained with more traditional Lorentzian-type approaches

Intrinsic proton states around the superdeformed shell closure Z=80

info:eu-repo/semantics/publishe

Investigation of a light Dark Boson existence: The New JEDI project

International audienceSeveral experiments around the world are looking for a new particle, named Dark Boson, which may do the link between the Ordinary Matter (which forms basically stars, planets, interstellar gas...) and the Hidden Sectors of the Universe. This particle, if it exists, would act as the messenger of a new fundamental interaction of nature. In this paper, the underlying Dark Sectors theory will be introduced first. A non-exhaustive summary of experimental studies carried out to date and foreseen in the incoming years will be presented after,including the 8Be anomaly. The last section will provide a status of the New JEDI**** project which aims to investigate the existence or not of a Dark Boson in the MeV range

Investigation of a light Dark Boson existence: The New JEDI project

International audienceSeveral experiments around the world are looking for a new particle, named Dark Boson, which may do the link between the Ordinary Matter (which forms basically stars, planets, interstellar gas...) and the Hidden Sectors of the Universe. This particle, if it exists, would act as the messenger of a new fundamental interaction of nature. In this paper, the underlying Dark Sectors theory will be introduced first. A non-exhaustive summary of experimental studies carried out to date and foreseen in the incoming years will be presented after,including the 8Be anomaly. The last section will provide a status of the New JEDI**** project which aims to investigate the existence or not of a Dark Boson in the MeV range

Investigation of a light Dark Boson existence: The New JEDI project

International audienceSeveral experiments around the world are looking for a new particle, named Dark Boson, which may do the link between the Ordinary Matter (which forms basically stars, planets, interstellar gas...) and the Hidden Sectors of the Universe. This particle, if it exists, would act as the messenger of a new fundamental interaction of nature. In this paper, the underlying Dark Sectors theory will be introduced first. A non-exhaustive summary of experimental studies carried out to date and foreseen in the incoming years will be presented after,including the 8Be anomaly. The last section will provide a status of the New JEDI**** project which aims to investigate the existence or not of a Dark Boson in the MeV range