Search results for "nuclear structure"
showing 10 items of 401 documents
Solar neutrino detection in liquid xenon detectors via charged-current scattering to excited states
2020
We investigate the prospects for real-time detection of solar neutrinos via the charged-current neutrino-nucleus scattering process in liquid xenon time projection chambers. We use a nuclear shell model, benchmarked with experimental data, to calculate the cross sections for populating specific excited states of the caesium nuclei produced by neutrino capture on $^{131}$Xe and $^{136}$Xe. The shell model is further used to compute the decay schemes of the low-lying $1^{+}$ excited states of $^{136}$Cs, for which there is sparse experimental data. We explore the possibility of tagging the characteristic de-excitation $\gamma$-rays/conversion electrons using two techniques: spatial separation…
Stability of the heaviest elements: K isomer in No250
2020
Decay spectroscopy of No250 has been performed using digital electronics and pulse-shape analysis of the fast nuclear decays for the first time. Previous studies of No250 reported two distinct fission decay lifetimes, related to the direct fission of the ground state and to the decay of an isomeric state but without the possibility to determine if the isomeric state decayed directly via fission or via internal electromagnetic transitions to the ground state. The data obtained in the current experiment allowed the puzzle to finally be resolved, attributing the shorter half-life of t1/2=3.8±0.3μs to the ground state and the longer half-life t1/2=34.9−3.2+3.9μs to the decay of an isomeric stat…
Isospin symmetry in B(E2) values: Coulomb excitation study of Mg21
2019
The Tz=−32 nucleus 21Mg has been studied by Coulomb excitation on 196Pt and 110Pd targets. A 205.6(1)-keV γ-ray transition resulting from the Coulomb excitation of the 52+ ground state to the first excited 12+ state in 21Mg was observed for the first time. Coulomb excitation cross-section measurements with both targets and a measurement of the half-life of the 12+ state yield an adopted value of B(E2;52+→12+)=13.3(4) W.u. A new excited state at 1672(1) keV with tentative 92+ assignment was also identified in 21Mg. This work demonstrates a large difference in the B(E2;52+→12+) value between T=32, A=21 mirror nuclei. The difference is investigated in the shell-model framework employing both i…
Precision mass measurements of Fe67 and Co69,70 : Nuclear structure toward N=40 and impact on r -process reaction rates
2020
Accurate mass measurements of neutron-rich iron and cobalt isotopes $^{67}\mathrm{Fe}$ and $^{69,70}\mathrm{Co}$ have been realized with the JYFLTRAP double Penning-trap mass spectrometer. With novel ion-manipulation techniques, the masses of the $^{69,70}\mathrm{Co}$ ground states and the $1/{2}^{\ensuremath{-}}$ isomer in $^{69}\mathrm{Co}$ have been extracted for the first time. The measurements remove ambiguities in the previous mass values and yield a smoother trend on the mass surface, extending it beyond $N=40$. The moderate $N=40$ subshell gap has been found to weaken below $^{68}\mathrm{Ni}$, a region known for shape coexistence and increased collectivity. The excitation energy for…
Understanding the nuclear structure of heavy elements
2013
The study of heavy and superheavy elements has always been one of the cornerstones of nuclear physics studies. These studies are driven by a desire to create new elements and to determine the limits of nuclear stability. Current experiments to synthesize new elements aim at the fabled ?Island of Stability? which should be found in the region of the next ?magic? numbers for protons and neutrons beyond Z?=?82 and N?=?126 (208Pb). The island is predicted to be around proton number 114?126 and neutron number 184. In recent years, another approach to understanding heavy nuclear systems has gained momentum, whereby nuclei with a much lower proton number of around 100 are studied in detail. The mo…
Quasifission in heavy and superheavy element formation reactions
2016
Superheavy elements are created in the laboratory by the fusion of two heavy nuclei. The large Coulomb repulsion that makes superheavy elements decay also makes the fusion process that forms them very unlikely. Instead, after sticking together for a short time, the two nuclei usually come apart, in a process called quasifission. Mass-angle distributions give the most direct information on the characteristics and time scales of quasifission. A systematic study of carefully chosen mass-angle distributions has provided information on the global trends of quasifission. Large deviations from these systematics reveal the major role played by the nuclear structure of the two colliding nuclei in de…
Halo effective field theory analysis of one-neutron knockout reactions of Be11 and C15
2021
Background: One-nucleon knockout reactions provide insightful information on the single-particle structure of nuclei. When applied to one-neutron halo nuclei, they are purely peripheral, suggesting that they could be properly modeled by describing the projectile within a halo effective field theory (halo-EFT).Purpose: We reanalyze the one-neutron knockout measurements of $^{11}\mathrm{Be}$ and $^{15}\mathrm{C}$---both one-neutron halo nuclei---on beryllium at about 60 MeV/nucleon. We consider halo-EFT descriptions of these nuclei which already provide excellent agreement with breakup and transfer data.Method: We include a halo-EFT description of the projectile within an eikonal-based model …
Coulomb dissociation of P 27 at 500 MeV/u
2016
J. Marganiec et al. ; 15 págs.; 14 figs.; 6 tabs.
Highly deformed bands in Nd nuclei: New results and consistent interpretation within the cranked Nilsson-Strutinsky formalism
2019
International audience; Three new highly-deformed (HD) bands are identified in Nd136 and the highly deformed band of Nd137 is extended at higher spin by four transitions, revealing a band crossing associated with the occupation of the second νi13/2 intruder orbital. Extended cranked Nilsson-Strutinsky calculations are performed for all HD bands observed in Nd134, Nd136, and Nd137, achieving for the first time a consistent interpretation of all HD bands in the Nd nuclei. The new interpretation has significant consequences, like the change of parity of the yrast HD bands of Nd134 and Nd136, and the involvement of two negative-parity neutron intruder orbitals in the configurations of most HD b…
Weak charge and weak radius of C12
2020
We present a feasibility study of a simultaneous subpercent extraction of the weak charge and the weak radius of the $^{12}\mathrm{C}$ nucleus using parity-violating electron scattering, based on a largely model-independent assessment of the uncertainties. The corresponding measurement is considered to be carried out at the future MESA facility in Mainz with ${E}_{\mathrm{beam}}=155\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$. We find that a combination of a 0.3% precise measurement of the parity-violating asymmetry at forward angles with a 10% measurement at backward angles will allow to determine the weak charge and the weak radius of $^{12}\mathrm{C}$ with 0.4% and 0.5% precision, respectiv…