Radiative Decay of Neutron-Unbound Intruder States in $^{19}$O

TL;DR

This study investigates gamma-ray decays from excited states of $^{19}$O above the neutron separation energy, revealing new decay modes and emphasizing the importance of diverse experimental methods for understanding nuclear structure.

Contribution

First observation of gamma decays from six neutron-unbound states in $^{19}$O, highlighting the competition between electromagnetic and neutron decay modes.

Findings

Gamma decays observed from six states above neutron separation energy.

Electromagnetic decay competes with neutron decay due to angular momentum barriers.

Results suggest higher spin and complex structure of intruder states.

Abstract

The $^{9}$Be($^{14}$C, $\alpha$$\gamma$) reaction at E$_{Lab}$=30 and 35 MeV was used to study excited states of $^{19}$O. The Florida State University (FSU) $\gamma$ detector array was used to detect $\gamma$ radiation in coincidence with charged particles detected and identified with a silicon $\Delta$E-E particle telescope. Gamma decays have been observed for the first time from six states ranging from 368 to 2147 keV above the neutron separation energy (S$_{n}$=3962 keV) in $^{19}$O. The $\gamma$ decaying states are interspersed among states previously observed to decay by neutron emission. The ability of electromagnetic decay to compete successfully with neutron decay is explained in terms of neutron angular momentum barriers and small spectroscopic factors implying higher spin and complex structure for these intruder states. These results illustrate the need for complementary experimental approaches to best illuminate the complete nuclear structure.