Nuclear lifetimes inAr42

Abstract

Excitation energies and nuclear lifetimes of states in "Ar have been measured by employing the reaction ' Ar(t, p)"Ar at a triton bombarding energy of 2.8 MeV. Protons were detected by an annular silicon surface barrier counter at an average angle of 174', and coincident y rays were detected by a 2&em' Ge(Li) counter positioned at angles of 30 and 120 . The extraction of nuclear lifetimes by the Doppler-shift-attenuation technique was made possible by the use of a solid argon target operated at 15 K. Experimental results for excitation energies (keV) and lifetimes (psec) are:

Shape ofAr44: Onset of deformation in neutron-rich nuclei nearCa48Zielińska1, Goergen2, Clément3 et al. 2009Phys. Rev. C2711570View full textAdd to dashboardCite

“…The erosion of the shell closure and the development of deformation for the proton-deficient N = 28 isotones was also predicted by Skyrme Hartree-Fock and relativistic mean-field (RMF) calculations [10,11]. Fully self-consistent relativistic HartreeBogoliubov calculations predicted a staggering of the groundstate deformation between oblate in 46 Ar and 42 Si and prolate in 44 S and 40 Mg, while the absolute deformation was found to increase with decreasing proton number [12]. Spectroscopic properties of N = 28 isotones were calculated using the angular momentum projected generator coordinate method with the axial quadrupole moment as generator coordinate and the Gogny D1S interaction [13].…”

“…The nuclear shape changes rapidly not only with the proton but also with the neutron number in this region of the nuclear chart. Spectroscopic results in the neutron-rich sulfur isotopes, for example, are consistent with a transition from prolate deformation in 40 S via γ softness in 42 S to prolate-oblate shape coexistence in 44 S [14]. This interpretation is supported by Hartree-Fock-Bogoliubov based configuration mixing calculations using a five-dimensional collective Hamiltonian and the Gogny D1S interaction [14,15].…”

“…With the modified interaction, SDPF-NR, the shell-model calculations found an increase of the 2p-2h intruder configuration for the ground-state wave functions in the N = 28 isotones. The intruder configuration was predicted to become dominant in the ground state of 40 Mg. However, the calculations still found a rather high excitation energy of 1.49 MeV for the 2 + 1 state in 42 Si [36].…”

“…These calculations predict that oblate shapes become favored in the N = 30 isotope 46 42 Si [6], while a measurement of the B(E2) value for this nucleus is presently out of reach. The dripline nucleus 40 Mg, finally, was recently observed for the first time by identifying three events in a fragmentation experiment [18]. The measurement of the energy and excitation probability of the first excited state gives a first indication of the collectivity of a nucleus.…”

“…Spectroscopic properties of N = 28 isotones were calculated using the angular momentum projected generator coordinate method with the axial quadrupole moment as generator coordinate and the Gogny D1S interaction [13]. These calculations predicted the onset of deformation for 46 Ar and the coexistence of welldeformed oblate and prolate shapes in the lighter isotones, with oblate shapes favored in 44 S and 42 Si and prolate deformation dominating in 40 Mg. The nuclear shape changes rapidly not only with the proton but also with the neutron number in this region of the nuclear chart.…”