New results on the decay spectroscopy of ²⁵⁴No with GABRIELA@SHELS

Abstract The structure of the 102 254 No 152 nucleus has been studied for more than 20 years: last publications on its decay spectroscopy are from LBNL [1], GSI [2], JYFL [3] and ANL [4]. Four schemes featuring two isomers have published interpreted differently in terms excitation energy scheme 2 nd isomer configuration assignments both K-isomers. These discrepancies triggered new experiments including this one, performed with GABRIELA [5, 6] array, at focal plane SHELS [7] separator FLNR, Dubna. first part proceeding will present experimental setup analysis techniques used to reveal electromagnetic known 254 No. second focus results obtained 1 million No nuclei implanted detector. In particular, internal conversion electron spectrum observed 8 − K-isomer revealed presence a strong transition, most likely E0, suggesting low-lying shape coexistence as predicted [8, 9]. γ-ray short-lived 170 μ s lines putting doubt previous interpretations about decay.