Lifetime measurements of states of 35S, 36S, 37S, and 38S using the AGATA γ-ray tracking spectrometer

Lifetimes or lifetime limits of a small number of excited states of the sulfur isotopes with mass numbers A = 35, 36, 37, and 38 have been measured using the differential recoil-distance method. The isotopes of sulfur were populated in binary grazing reactions initiated by a beam of S-36 ions of energy 225 MeV incident on a thin Pb-208 target which was mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA gamma-ray tracking array was used to detect gamma rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were measured within the range from about 1 to 100 ps. The number of states for which lifetime measurements or lifetime limits were possible was limited by statistics. For S-35, the lifetime was determined for the first 1/2(+) state at 1572 keV; the result is compared with a previous published lifetime value. The lifetime of the 3(-) state of S-36 at 4193 keV was determined and compared with earlier measurements. No previous lifetime information exists for the (6(+)) state at 6690 keV; a lifetime measurement with large associated error was made in the present work. For S-37, the states for which lifetime limits were established were those at 646 keV with J(pi)=3/2(-) and at 2776 keV with J(pi)=11/2(-); there are no previously published lifetime values for excited states of 37S. Finally, a lifetime limit was established for the J(pi )= (6(+)) state of S-38 at 3675 keV; no lifetime information exists for this state in the literature. Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF, SDPF-U, and FSU effective interactions. In addition, nuclear magnetic-dipole and electric-quadrupole moments, branching ratios, mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. The current work suffers from poor statistics; nevertheless, lifetime values and limits have been possible, allowing a useful discussion of the ability of state-of-the-art shell-model calculations to reproduce the experimental results.

Automated summary

This study measured the lifetimes or lifetime limits of excited states of sulfur isotopes using the differential recoil-distance method. By comparing the results with state-of-the-art shell-model calculations, the ability of reproducing the experimental results was discussed.