γ-ray spectroscopy of neutron-richS40

Abstract

Yrast states up to (6 + ) in the neutron-rich 40 S nucleus have been studied using binary grazing reactions produced by the interaction of a 215 MeV beam of 36 S ions with a thin 208 Pb target. The novel experimental setup that combines the large acceptance magnetic spectrometer, PRISMA, and the high-efficiency γ -ray detection array, CLARA, was used. A new γ -ray transition at an energy of 1572 keV was observed and tentatively assigned to the (6 + ) → (4 + ) transition. A comparison of experimental observations and the results of large-scale 0hω sd-pf shell-model calculations indicates that one-and two-proton excitations from the 2s 1/2 to the 1d 3/2 orbitals play an important role in reproducing the 40 S yrast level structure and the published B(E2; 0 + g.s. → 2 + 1 ) value. The structure of the yrast states of the even-A isotopes of sulfur is interpreted in terms of the configurations of valence protons and neutrons within the context of large-scale 0hω sd-pf shell-model calculations.

In-beam γ -ray spectroscopy of S38–42

“…[ We observe strong transitions at 1292(4), 1515(6), and 1534(5) keV that can be identified with the previously reported 2 [18,20,[33][34][35]. This is consistent with the coincidence spectra shown in Fig.…”

“…The 833(5) keV transition in our spectrum is 16 keV lower than the (6 + 1 ) → 4 + 1 transition previously reported at 849 keV [18,20]. Given the velocity of the S reaction residues, v/c ∼ 0.35, and the C target thickness of 149 mg/cm 2 , excited states with lifetimes of the order of several tens to hundreds of picoseconds will predominantly decay downstream of the target, signaled by a lowered peak energy and a left-tail in the Dopplerreconstructed γ-ray spectrum.…”

“…Here, we report on the in-beam γ-ray spectroscopy of 38−42 S following the fragmentation of 46 Ar and 48 Ca intermediate-energy projectile beams on a C target in the center of the GRETINA γ-ray spectrometer [24]. Complementing the comparisons by Wang et al [18] of S level schemes to shell-model calculations with the SDPF-U effective interaction [25], we compare our measurements with similar calculations based on the SDPF-MU Hamiltonian, which was constructed to describe the shell and shape evolution in the S and Si isotopic chains as N = 28 is approached [3].…”

“…Gamma-ray spectroscopy following, for example, β decay [19], intermediate-energy Coulomb excitation [14], multinucleon transfer reactions [17,18,20], and projectile fragmentation [15,16] provided a first, limited glimpse of the level structure of the neutron-rich S isotopes approaching N = 28 [23]. Here, we report on the in-beam γ-ray spectroscopy of 38−42 S following the fragmentation of 46 Ar and 48 Ca intermediate-energy projectile beams on a C target in the center of the GRETINA γ-ray spectrometer [24].…”

“…These effects are included in the SDPF-MU effective shell-model interaction introduced in [3] and the resulting predictions for the 40,41,42 S level schemes will be tested in the present work. The sulfur isotopes between N = 20 and N = 28 have been studied with a variety of experimental techniques [10][11][12][13][14][15][16][17][18][19][20], however, information on the level schemes even at low excitation energy is still scarce. Beyond N = 28, very few excited states have been reported in the S isotopic chain [21,22].…”