Lifetime measurement of the 68Ga 7(-) isomeric state

by Mr Rafael Escudeiro (Università di San Paolo)

Friday 26 Oct 2018, 11:30 → 12:30 Europe/Rome

M.B. Ceolin meeting room (INFN-LNL)

Isomeric nuclear states are those excited states which decay with long lifetimes (T1/2 > 10 ns); their study generally reveals, a large change in angular momentum in its decay, a small matrix element or a small transition energy [1]. By measuring lifetimes of isomeric states it is possible to obtain information about this state’s wave function, being a robust test for nuclear models. In this work, a system developed at the Laboratório Aberto de Fı́sica Nuclear (LAFN) of University of São Paulo called System for the Measurement of Isomeric States (SISMEI) was utilized [2]. Delayed coincidence between evaporated particles in a nuclear reaction and the delayed gamma-rays emitted from the isomeric state was used to measure lifetimes [3]. An experiment to measure the 7(−) (E = 1229.87(4) keV) isomeric state of 68Ga was performed. The experiment took about 80 hours with an event rate of about 8 × 10^{^4} counts per second. The measured value was T 1/2 = 60.8(11) ns, which is compatible with experimental results obtained from other authors [4]. The nuclear structure of this nucleus was calculated with the Large Scale Shell Model by using two different residual interactions; the results were compared with the known values [4]. [1] G. D. Dracoulis, Physica Scripta, vol. T152, no. 014015, 2013.
[2] D. L. Toufen et al., Rev. Sci. Instrum., vol. 85, no. 073501, pp. 437–443, 2014.
[3] H. Morinaga, In-Beam Gamma-Ray Spectroscopy. North-Holland Publishing Company, 1976.
[4] E. McCutchan, Nuclear Data Sheets,vol. 113, pp. 1735–1870, 2012.