Beta Delayed Spectroscopy of 29F, observation of the first excited state of 29Ne

The island of inversion around 32Mg, characterized by tensor-force-driven deformation, has

been well characterized in its north and west “shores.” The south-eastern “beaches” offer

intriguing physics where deformation and neutron dripline effects overlap, yet they remain

poorly known due to the difficulty in producing them in experimental facilities. In particular, if

standard ordering is restored at the dripline, it will suppress low-energy opposite-parity

intruders.

In this talk, I will present experimental work done at the

National Superconducting Laboratory as a part of the E19044 collaboration. A 48Ca beam

was fragmented to produce a cocktail beam of isotopes around Z=9, N=20 29F and

separated by mass using the A1900 spectrometer. The cocktail beam was implanted in a

YSO crystal, and the decay products were detected using 3 HPGe clovers for gamma rays

and 48 VANDLE bars for beta delayed neutrons.

This presentation will focus on beta-delayed gamma and neutron spectroscopy of 29F. We have observed for the first time a gamma transition at 174 keV. From the observed beta feeding we deduce it corresponds to a Gamow-Teller transition, which we interpret as the first excited state of 3/2+ spin parity. Our measurement supports a 3/2- 29Ne ground state, thus likely being in the island of inversion, as previously indicated by several reaction experiments (A. Revel 2023, N. Kobayashi 2016, H.N. Liu 2017)