In-beam spectroscopy of 215Rn86

Abstract

The yrast level structure of 215Rn has been studied by means of in-beam spectroscopy α-γ-γ coincidence techniques through the 207Pb(18O,2α2n) reaction at 93 MeV bombarding energy, using the 8π GASP-ISIS spectrometer at Legnaro. New spectroscopic information has been obtained. The deduced low-lying level scheme of 215Rn does not exhibit the alternating parity structure observed in the heavier known isotones 216Fr, 217Ra, 218Ac, and 219Th. From this result, the lightest nucleus showing evidence for octupole collectivity is 216Fr, defining the lowest-mass corner for this kind of phenomenon as N≥129 and Z≥87.