Lifetime measurements of states of $^{35}\mathrm{S}$, $^{36}\mathrm{S}$, $^{37}\mathrm{S}$, and $^{38}\mathrm{S}$ using the AGATA $\gamma$-ray tracking spectrometer
Résumé
Lifetimes or lifetime limits of a small number of excited states of the sulfur isotopes with mass numbers , 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 ions of energy 225 MeV incident on a thin target which was mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA -ray tracking array was used to detect 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 , the lifetime was determined for the first state at 1572 keV; the result is compared with a previous published lifetime value. The lifetime of the state of at 4193 keV was determined and compared with earlier measurements. No previous lifetime information exists for the () state at 6690 keV; a lifetime measurement with large associated error was made in the present work. For , the states for which lifetime limits were established were those at 646 keV with and at 2776 keV with ; there are no previously published lifetime values for excited states of . Finally, a lifetime limit was established for the state of 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.