Conveners
Proposals: Physics I
- Heather Crawford (Lawrence Berkeley National Laboratory)
Proposals: Physics II
- Nori AOI (RCNP, Osaka Univ.)
Proposals: Physics III
- Thorsten Kroell (TU Darmstadt)
Proposals: Physics IV
- Peter Reiter
Proposals: Physics V
- Anna Corsi (CEA Saclay)
Proposals: Physics VI
- Volker Werner (TU Darmstadt)
State-of-the-art beyond mean field methods with the Gogny D1S interaction has predicted for the N=Z $^{80}$Zr nucleus five 0$^+$ states corresponding to different nuclear shapes within 2.25 MeV, where several rotational and γ-bands are built upon those five 0+ states [1]. We propose to study the rich low-lying energy spectrum of $^{80}$Zr, by using a 1n and 2n knock-out reaction from...
Nuclear physicists have kept their attention to the nuclei that the proton number (Z) and the neutron number (N) are same, i.e. N=Z, because they are interesting for several reasons. First, they provide a test ground of exchange symmetry between protons and neutrons. Approximately, the nuclear force acting between nucleons does not distinguish the kind of nucleons. However, each proton has a...
Enhanced neutron-proton (np) pairing correlations can arise when both particle types occupy the same orbitals. In addition to the T = 1 np pairing phase, the opportunity for isoscalar (T = 0) correlations is also present, especially on the N=Z line. Competition between these np-pairing mechanisms is of much interest. Recent work on $^{92}$Pd [1] has indicated the possibility for the existence...
D. Bazzacco, A. Goasduff, S.M. Lenzi, S. Lunardi, R. Menegazzo, D. Mengoni, A. Montaner-Pizá, G. Pascualato, F. Recchia, D. Testov
Dipartimento di Fisica e Astronomia, Università di Padova and INFN Sezione di Padova, Padova, Italy
T. Bayram, A. Illana, G. de Angelis, D. Brugnara, M.L. Cortés, F. Galtarossa, A. Gottardo, E. Gregor, T. Marchi, D.R. Napoli, J.J. Valiente-Dobón, I. Zanon
*INFN...
Collectivity in nuclei in the vicinity of the N = Z line may be enhanced by neutron-proton
interactions occupying similar orbits near the Fermi level. Therefore, information on single-particle
energies and residual interactions with respect to the 100 Sn core are extremely important. The region
of 100 Sn has been extensively investigated due to unusual B(E2;0 + →2 + ) values observed for light...
The robustness of the proton and neutron shells for the doubly magic nucleus $^{100}$Sn has been studied in $\beta$-decay experiments, resulting in the smallest log $ft$ value for the decay of the $^{100}$Sn ground state to the $(1^+)$ state in $^{100}$In. A decay spectroscopy experiment at the RIBF has improved the statistical uncertainties on the corresponding Gamow-Teller decay strength...
D. Bazzacco, S. Lenzi, S. Lunardi, D. Mengoni, A. Montaner-Piza’,
A. Goasduff, R. Menegazzo, G. Pasqualato, F. Recchia, D. Testov
Dipartimento di Fisica, Universita’ di Padova and INFN (Italy)
P. Doornenbal, K. Wimmer
RIKEN Nishina Center (Japan)
T. Bayram, D. Brugnara, L. Cortes, G. de Angelis,
A. Gottardo, E. Gregor, A. Illana, D.R. Napoli, I. Zanon, J.J. Valiente Dobon
INFN Laboratori...
The seniority scheme was introduced by Racah, initially to identify multiparticle configurations in the atomic spectrum, latter was extended for the atomic nucleus, where is useful to classify the jn states in the jj-coupling. The concept of seniority in bound to the pairing. The seniority is generally conserved up to a large extend and it is well known the conditions that need to satisfy the...
A main focus of nuclear physics nowadays is the study of the evolution of shell structure in exotic isotopes. An interesting region of the nuclear chart to test shell evolution is around the Ni isotopic chain. For this chain, $B(E2;~0^+_{\mathrm{g.s.}}\rightarrow2^+_1)$ measurements have shown a behavior that differs, not only from the seniority scheme, but also from different theoretical...
One of the most compelling regions of the nuclear chart within reach of current experimental facilities is that of the N=40 isotopes near $^{64}$Cr. Due to the strong effect of the pn interaction between the protons and neutrons at the Fermi surface, the removal of $f_{7/2}$ protons below Ni effectively alters the $f_{5/2}$ neutron spin-orbit partner energy relative to the $g_{9/2}$ and...
We propose to perform the spectroscopy of N=51 isotones of 83Ge and 81Zn. The goal is to use the selectivity of neutron knockout from 84Ge and 82Zn to characterize the evolution of the ν(s1/2-d5/2) energy splitting and to identify for the first time (2p-1h) intruder state (ν(g9/2)-1(sd)+2 ) possible signature of shape coexistence above N=50 close to 78Ni. Such a study is uniquely possible at...
E2 Coulex measurements in $^{79,81}$Zn to understand nuclear intruder states and shell evolution
Introduction
Recent work [Delafosse] has pointed out that the physics around the N=50 shell closure close to $^{78}$Ni may be driven by the effects of ρ-meson exchange potential. On the one hand, this is causing a reduction of the N=50 gap going towards Z=32, inducing a sudden increase of...
Secondary knockout reactions and lifetime measurement with the plunger technique
Recent work [Delafosse] has pointed out that the physics around the N=50 shell closure close to $^{78}$Ni may be driven by the effects of $\rho$-meson exchange potential. This potential causes a reduction of the N=50 gap going towards Z=32, inducing a sudden increase of across-shell quadrupole coherence in...
Neutron rich Ge isotopes represent a puzzle so far as the few existing data
yield a contradicting picture. A recently determined large $B(E2;2^+ \to 0^+)$
value with a large uncertainty in $^{84}$Ge hints for a completely unexpected
shape transition from soft triaxiality in neutron rich Se isotopes with
Z=34 to prolate deformation for neighboring Ge with Z=32 [1]. Such an
"island of inversion"...
The evolution of collectivity, mirrored in B(E2) excitation strength, along the N=52 isotonic line is of special interest toward the Z=28 shell closure. The degree of collectivity depends on the possibility of cross-shell excitations, and on the evolution of shell structure in general. The energies of 21+ states in the N=52 isotones minimize at Z=32 (Ge), only four protons above the Z=28 magic...
The neutron-rich calcium isotopes have been a focus both experimentally and theoretically, as a key isotopic chain with clear examples of evolving shell structure and a test-bed for microscopically-based interactions and large-space $ab-initio$ calculations. While spectroscopy has extended quite far along the Ca isotopes, out to $^{56}$Ca at least, the evolution of single-particle occupancies...
The increase in collectivity in neutron-rich isotopes around N=40 has been attributed to the enhanced occupation of neutron intruder orbitals from above N=40 [1]. At the center of this island of inversion lies 64Cr. We propose to measure neutron and proton knockout from 64Cr to quantify the neutron g9/2 and d5/2 intruder orbital occupations. The proton knockout will yield the relative location...
We propose proton knockout from $^{64}$Cr to $^{63}$V. For a deformed ground state (as may be expected) the odd proton can be removed from low-lying Nilsson states for example the $\Omega = 3/2$ levels originating from the $d_{3/2}$ or $f_{7/2}$ shell model states. The spectroscopy will provide an important measure of the relative energies of the proton states, which is sensitive to the...
Beyond the new magic number N = 34, the region around the neutron-rich Ca isotopes, continues to attract a lot of attention. Recently, the energy of the first 2+ state of 56Ca was measured to have an unexpectedly high value [ChePC]. The excitation energies of the 2+ states of the N = 34 nuclei 56Ti and 52Ar indicate that the shell closure occurs only at and below Ca [Liu]. To clarify the...
We will are considering to propose experiments to clarify the anomalous structures in the neutron rich nuclei around and beyond 132Sn in continuation of our previous study.
One of the interests is the decoupling between proton and neutron motion in the low-lying excited states of the nuclei around 132Sn. The other is the evolution of collectivity along Z~50 towards N~90. We are considering...
Isospin formalism, which describes the neutron and the proton as two states of the same particle, the nucleon, is amongst the essential descriptive tools of a broad range of nuclear phenomena. The success of the isospin symmetry concept belies its broken nature. Not only is the symmetry broken by the proton-neutron mass difference and the Coulomb interaction, but also by the nucleon-nucleon...
The understanding of the few-nucleon pair motions in an atomic nucleus is one of the ever-evolving topics for the many-body quantum system within a finite potential space. The Te nuclide with $N$ > 82 is the best laboratory to investigate the motion and interaction of a single proton pair in the neutron-rich environment like helium over the robustly closed core of $^{132}$Sn. The neutron-rich...
The evolution of pairing correlations in exotic nuclei is a subject which has received much attention in recent years, as RIB’s accelerator facilities are providing unique isotopes to study. Of particular interest is the role of pairing in neutron-rich systems where the appearance of a low-density surface may induce a transition from the well known BCS Cooper-pairing mechanism to a BEC...
129Ag is a single magic N=82 nucleus. With three protons holes below 132Sn is neutron-rich, and any experimental information to be obtained on its structure is directly applicable for the understanding of lighter N=82 nuclei on the r-process waiting path. Proton knockout from 130Cd on the MINOS liquid hydrogen target will be used to populate 129Ag.
130Cd in it is ground-state has two proton...
Compared to studies of neutron-rich nuclei (A,Z) employing isomeric decay or Coulomb
excitation which require the isotope of interest as secondary beam or spectroscopy
following β-decay which even requires the more neutron-rich (A,Z-1) isotope, (p,2p)
reactions start from the less exotic isotope (A+1,Z+1). This reaction mechnism has been
exploited successfully already in the SEASTAR campaign...
With this proposal we intend to continue our experimental program to study neutron-rich nuclei in the region around doubly-magic 132Sn using in-beam γ-ray spectroscopy at relativistic energies, which we initiated with experiment NP1306-RIBF98R1 in 2015. In particular, we propose to study the octupole deformation of neutron-rich Ba isotopes by measuring the transition probabilities to the first...
The quadrant of the nuclear chart north-east of the doubly magic $^{78}$Ni is expected to be rife with competition between single-particle and collective degrees of freedom. Of the nuclei in the $28\lt Z<50$ and $50\lt N<82$ valence spaces, the neutron-rich Se isotopes have been suggested by theory and experiment to exhibit shape co-existence of spherical, prolate and oblate shapes, and prone...
Even-even strontium and zirconium nuclei in the A=100 region show a sudden onset of deformation at N=60 while the lighter isotopes up to N=58 are rather spherical. Unlike, the even krypton isotopes exhibit a smooth onset of collectivity up to N=60 [1]. Recent high-resolution gamma-spectroscopy results on 96Kr [2] following projectile fission confirmed the energy of the yrast 2+ --> 0+...
More than 40 years have passed since the first discovery of the island of inversion [1]. In the
shell model point of view the phenomenon is attributed to the change of the effective single
particle energy, which gives rise to the quenched N=20 shell gap [2]. On the other hand the
single particle structures of 31Mg [3] and 33Mg [4] can be well understood in the Nilsson
diagram, which suggests...
Nuclear moment measurements of short lived excited states are in general very challenging due to the requirement to obtain strong enough magnetic fields, capable to provide a sizeable perturbation of the nuclear spin ensemble within the lifetime of the state of interest. Kilotesla’s magnetic fields are usually needed for nuclear states of picosecond lifetimes. Hyperfine fields were often...
