The Gamow Shell Model (GSM) is an open-quantum system extension of the traditional Shell Model. By treating correlations and continuum effects on the same footing, it provides a framework to describe low-lying states, whether they are bound or resonant. So far, the use of schematic two-body interactions has delivered solid proofs of principles for GSM with the description of various exotic nuclear features such as halo structures, cigar/dineutron configurations or states described as antibound.
In this seminar, I will discuss the GSM description of the so-called stretched single-particle states, which are high-energy states dominated by a single particle-hole component between two distant shells. The focus will be put on the M4 state in 13C located at an excitation energy of 21.47 MeV, which has a tentative experimental spin of 7/2+ or 9/2+. This M4 state decays by the emission of protons and neutrons (with a total width of ~270 keV) and is thus a good testing ground for continuum models such as the GSM. Its decay was recently measured at the Cyclotron Centre Bronowice (CCB) and is currently being analyzed by the local experimental group at IFJ-PAN. In this seminar, I will present the first GSM description (and spin assignment) of this M4 resonant state, its theoretical relative decay scheme to the daughter states in 12C and 12B, as well as comparisons to the newly measured experimental data.