Search results for "collectivity"
showing 8 items of 8 documents
High-Statistics Sub-Barrier Coulomb Excitation of $^{106,108,110}$Sn
2020
International audience; A Coulomb excitation campaign on $^{106,108,110}$Sn at 4.4–4.5 MeV/u was launched at the HIE-ISOLDE facility at CERN. Larger excitation cross sections and γ-ray statistics were achieved compared to previous experiments at ∼2.8 MeV/u. More precise $(B(E2;0_{1}^{ + } \to 2_{1}^{ + }))$ values, lifetimes of states via the Doppler shift attenuation method, and new $(B(E2;0_{1}^{ + } \to 2_{x}^{ + })), (B(E2;2_{1}^{ + } \to 4_{1}^{ + }))$ and $(Q(2_{1}^{ + }))$ values from the new Miniball data will be obtained and applied to test modern nuclear structure theories.
Collectivity in the light radon nuclei measured directly via Coulomb excitation
2015
Background: Shape coexistence in heavy nuclei poses a strong challenge to state-of-the-art nuclear models, where several competing shape minima are found close to the ground state. A classic region for investigating this phenomenon is in the region around Z=82 and the neutron midshell at N=104. Purpose: Evidence for shape coexistence has been inferred from α-decay measurements, laser spectroscopy, and in-beam measurements. While the latter allow the pattern of excited states and rotational band structures to be mapped out, a detailed understanding of shape coexistence can only come from measurements of electromagnetic matrix elements. Method: Secondary, radioactive ion beams of Rn202 and Rn…
Testing microscopically derived descriptions of nuclear collectivity: Coulomb excitation of Mg-22
2018
Many-body nuclear theory utilizing microscopic or chiral potentials has developed to the point that collectivity might be dealt with in an {\it ab initio} framework without the use of effective charges; for example with the proper evolution of operators, or alternatively, through the use of an appropriate and manageable subset of particle-hole excitations. We present a precise determination of $E2$ strength in $^{22}$Mg and its mirror $^{22}$Ne by Coulomb excitation, allowing for rigorous comparisons with theory. No-core symplectic shell-model calculations were performed and agree with the new $B(E2)$ values while in-medium similarity-renormalization-group calculations consistently underpre…
Single-particle and collective excitations in the transitional nucleus 166Os
2021
The mean lifetimes of the lowest energy 2+, 8+ and 9− states in 166Os have been measured using the recoil distance Doppler-shift method in conjunction with a selective recoil-decay tagging technique. These measurements extend studies into the most neutron-deficient mass region accessible to current experimental methods. The B(E2; 2+ → 0+) = 7(2) W.u. extracted from these measurements is markedly lower than those observed in the heavier even-mass Os isotopes. The 8+ and 9− states yield reduced transition probabilities that are consistent with single-particle transitions. While these values may indicate a departure from collective structure, the level scheme and the underlying nuclear configu…
Individuals and Collectivity between the Principle of noncontradiction and joint commitment
2017
In this paper I pay attention to and reflect upon the role and the nature of the human being considered as an individual that acts in a collective dimension and thus contributes to build a social reality. What is required to talk of collectivity? Is it anything that goes beyond the interacting individuals or not? In order to talk of collectivity, do we need to talk of a plural subject as well as of collective beliefs, (as Margaret Gilbert does), or not? These are some questions that are addressed in my paper. In particular, I outline the view that the collectivity is the relationship among interacting individuals in the exercise of their own rationality. Consequently, I argue that the colle…
Collectivity along N=50: Nuclear Structure studies on the neutron-magic nuclei 92Mo and 94Ru with AGATA and VAMOS++
2019
El trabajo desarrollado en esta Tesis se centra en estudio experimental del comportamiento colectivo de los estados excitados de los núcleos semimágicos con N=50 en función de la ocupación del orbital g9/2 de protones, a través de la medida de la vida media de los estados "yrast" 4+ de los núcleos 92Mo y 94Ru. En particular, se ha investigado la conservación de "seniority" a lo largo de la capa g9/2 que es la primera capa donde podría no conservarse. El 100Sn, siendo el núcleo doblemente mágico ligado más pesado con igual número de protones y neutrones, ha atraído siempre un considerable interés desde el punto de vista experimental y teórico. La estructura de este núcleo y sus vecinos son e…
Electromagnetic moments of scandium isotopes and $N=28$ isotones in the distinctive $0f_{7/2}$ orbit
2022
The electric quadrupole moment of $^{49}$Sc was measured by collinear laser spectroscopy at CERN-ISOLDE to be $Q_{\rm s}=-0.159(8)$ $e$b, and a nearly tenfold improvement in precision was reached for the electromagnetic moments of $^{47,49}$Sc. The single-particle behavior and nucleon-nucleon correlations are investigated with the electromagnetic moments of $Z=21$ isotopes and $N=28$ isotones as valence neutrons and protons fill the distinctive $0f_{7/2}$ orbit, respectively, located between magic numbers, 20 and 28. The experimental data are interpreted with shell-model calculations using an effective interaction, and ab-initio valence-space in-medium similarity renormalization group calcu…
Charge radii of neon isotopes across the sd neutron shell
2011
We report on the changes in mean square charge radii of unstable neon nuclei relative to the stable Ne-20, based on the measurement of optical isotope shifts. The studies were carried out using collinear laser spectroscopy on a fast beam of neutral neon atoms. High sensitivity on short-lived isotopes was achieved thanks to nonoptical detection based on optical pumping and state-selective collisional ionization, which was complemented by an accurate determination of the beam kinetic energy. The new results provide information on the structural changes in the sequence of neon isotopes all across the neutron sd shell, ranging from the proton drip line nucleus and halo candidate Ne-17 up to the…