Seminar Details

Recent β-decay Studies of 100Sn

Kortney Cooper, MSU - NSCL/Chemistry
Thursday, January 31, 11:00 AM - Research Discussion
NSCL Lecture Hall

Determination of the limits of stability has been a focus of nuclear science for many years. An important experimental tool to study these exotic nuclei is the observation of their beta decay and associated radiations. The nuclear shell model is a central theoretical tool for the study of exotic nuclei, in particular establishing the validity of the predicted ‘closed shells’ far from stability. 100Sn is a long sought, doubly closed-shell isotope of tin that until recently has remained inaccessible to detailed study due to production limitations. Not only is 100Sn predicted to be the heaviest doubly-magic, N=Z nucleus that is stable against proton decay, but the strength of its beta decay will provide new information on its unique nuclear structure [1-2]. Early experiments [3-5] were only able to produce a few 100Sn nuclei during week-long experiments. The recent work of Hinke et al. [1] increased the number of observed 100Sn nuclei by more than a factor of ten. A total of 259 100Sn nuclei were detected, with a decay measurement of 126 of those nuclei. These improved statistics, resulted in a more precise half-life value of 1.16 ± 0.20s. For the first time, the beta-decay end-point energy was reported to be 3.29 ± 0.20 MeV, and gamma-ray transitions were observed from the de-excitation of the daughter nucleus, 100In. Finally, and maybe the most significant result, the log(ft) value was deduced to be 2.62 +0.13,-0.12. This small value of log(ft) classifies the Gamow-Teller beta decay of 100Sn (0+) to 100In (1+) as “superallowed”, which is a term usually reserved for Fermi (0+-0+) decays. The experimental details of searches for this isotope and the conclusions of the recent work will be discussed. References: 1. C. B. Hinke et al., Nature 486, 341 (2012) 2. B. A. Brown and K. Rykaczewski, Phys. Rev. C 50, R2270 (1994) 3. R. Schneider et al., Nuclear Phys. A 588, 191c (1995) 4. M. Lewitowicz et al., Phys. Letters B 332, 20 (1994) 5. D. Bazin et al., Phys. Rev. Letters 101, 252501 (2008)