$\gamma$ decay from the near-neutron-threshold $2^{+}$ state in $^{14}C$: A probe of collectivization phenomena in light nuclei.

Corbari G., Bottoni S., Ciemala M., Crespi F.C.L., Leoni S., Fornal B., Janssens R.V.F., Pain S.D., Siciliano M.
  Giovedì 15/09   15:00 - 18:30   Aula B - Maria Goeppert-Mayer   I - Fisica nucleare e subnucleare   Presentazione
Light nuclei, with mass $A<20$, are among the best probes of most advanced nuclear theory models. Of particular interest are near-threshold states, $i.e.$, narrow resonances lying in proximity of particle-emission thresholds. According to theory, the existence of near-threshold states is a universal phenomenon, and their structure should provide relevant information on the microscopic mechanism leading to the onset of clusterization phenomena in molecular-like nuclei, $e.g.$, C, O, $Ne\ldots$\ . So far, the decay properties of near-threshold states in neutron-rich systems have been poorly explored, and almost uniquely via particle spectroscopy. The $\gamma$-decay branch is in fact at the level of $10^{-3}\mbox{--}10^{-5}$ of the dominant particle-decay mode, $i.e.$, below the detection capabilities of conventional $\gamma$-ray spectrometers. In this contribution we will present preliminary results from a first experiment performed at Argonne (USA) with the GRETINA tracking array, aiming at the investigation of the $\gamma$ decay of the second $2^{+}$ in $^{14}C$, located at $8318 {keV}$, $i.e.$, $142 {keV}$ above the neutron-decay threshold. Comparison with model predictions will be also discussed.