Laser-assisted decay spectroscopy and mass spectrometry of Au 178

Abstract

A comprehensive study of the isotope Au178 has been made at the CERN-ISOLDE facility, using resonance laser ionization. Two long-lived states in Au178 were identified - a low-spin ground state and a high-spin isomer - each of which were produced as pure beams. Using the ISOLTRAP precision Penning trap, the excitation energy of the isomeric state in Au178 was determined to be E∗=189(14)keV. The α-decay fine structure patterns of the two states were studied using the Windmill decay station, providing information on the low-lying states in the daughter nucleus Ir174. Nuclear spin assignments of I(Aug178)=(2,3) and I(Aum178)=(7,8) are made based on the observed β-decay feeding and hyperfine structure intensity patterns. These spin assignments are used for fitting the hyperfine structures of the two states from which values for the magnetic dipole moments are extracted. The extracted moments are compared with calculations using additivity relations to establish the most probable configurations for Aug,m178.