Towards In-beam Spectroscopy of the Heaviest Nuclei with Gammasphere and AGFA

Spectroscopy of trans-fermium nuclei around the Z=100 and N=152 deformed shell gaps has been an active area of research at the ATLAS facility at Argonne National Laboratory for many years since the pioneering experiments which led to the observation of a rotational band and K-isomers in ²⁵⁴No using the Gammasphere gamma-ray detector array and the Fragment Mass Analyzer (FMA). Rotational bands and K-isomers in trans-fermium nuclei provide stringent tests of nuclear models used to describe properties of the heaviest elements such as for example their magic numbers which determine the location of the long sought after island of super-heavy nuclei. Recent highlights include first observation of two fast isomers in the heaviest known even-even N=150 isotone ²⁵⁴Rf employing the digital DAQ and the determination of the fission barrier in ²⁵⁴No from g-ray energy-spin distributions obtained with Gammasphere. To extend these studies to even heavier nuclei the Argonne Gas-filled Fragment Analyzer (AGFA) was designed and is currently being commissioned. Due to charge-state focusing AGFA has a factor of about ten higher efficiency compared to the FMA. Gammasphere combined with AGFA offer unparalleled opportunities for in-beam spectroscopic studies of trans-fermium nuclei. During the talk, first results obtained with AGFA and Gammasphere will be presented and prospects for in-beam spectroscopy of the heaviest nuclei will be discussed.