Fine structure in the decay of Hg and Au.

The -decay fine structure of Hg and Au was studied by means of decay spectroscopy. Two experiments were performed at the Accelerator Laboratory of the University of Jyväskylä (JYFL), Finland, utilizing the recoil separator RITU and a digital data acquisition system. The heavy-ion induced fusion-evaporation reactions Kr +  Ru and Kr +  Mo were used to produce the Hg and Au nuclei, respectively. Studying the evaporation residues (ER, recoils)- - correlations and -  coincidences, a new  decay with E  = 6156(10) keV was observed from Hg. This decay populates the (9/2 ) excited state at an excitation energy of 131.3(5) keV in Pt. The internal conversion coefficient for the 131.3(5) keV transition de-exciting this state was measured for the first time. Regarding the Au nucleus, a new  decay with E  = 5998(9) keV was observed to populate the 156.1(6) keV excited state in Ir. Two de-excitation paths were observed from this excited state. Moreover, a new 215.7(13) keV transition was observed to depopulate the 424.4(13) keV excited state in Ir. Properties of the Hg and Au  decays were examined in a framework of reduced widths and hindrance factors. For clarity and simplicity, the spin and parity assignments (e.g. ) are presented without brackets throughout the text.