Speaker
Description
The semi-magic $^{120}_{50}$Sn$_{70}$ lies in the neutron mid-shell among the other stable Sn isotopes, where $2p-2h$ intruder configurations built on excited 0$^+$ states have been recently observed. However, the transition rates from the $0^+_3$ state in $^{120}$Sn are not well-known because its lifetime only has a lower limit of 6 ps, which prevents a firm assignment or exclusion of the $0^+_3$ state into the intruder band.
The first thermal neutron capture experiment, $^{119}$Sn(n,$\gamma^\text{many}$)$^{120}$Sn, was performed at the Institut Laue-Langevin, where the world's highest-flux thermal neutron beam was delivered at $10^8$ n/cm$^2$/s at the target position on an isotopically enriched $^{119}$Sn target. Low-spin states in $^{120}$Sn were populated up to $S_n=9.1$ MeV, and the decaying gamma-ray cascades were detected with the Fission Product Prompt Gamma-ray Spectrometer (FIPPS) comprised of eight Compton-suppressed HPGe clovers coupled to an array of 15 LaBr$_3$(Ce) scintillation detectors. The LaBr$_3$(Ce) scintillators, which were used for gamma-ray detection and lifetime measurement using the Mirror Symmetric Centroid Difference (MSCD) method, have fast timing responses and are ideal for extracting lifetimes between 10 and a few hundred ps.
In total, there are $4\times10^9$ counts in the $\gamma\gamma\gamma$ cube where two LaBr$_3$(Ce) events were in coincidence with one HPGe. Preliminary lifetimes in $^{120}$Sn using the MSCD technique will be reported.
| Funding Agency | NSERC |
|---|---|
| Email Address | twa73@sfu.ca |
