Fine structure in the \(\upalpha \) decay of \(^{179}\)Hg and \(^{177}\)Au

Abstract

The \(\upalpha \)-decay fine structure of \(^{179}\)Hg and \(^{177}\)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 \(^{82}_{36}\)Kr + \(^{100}_{44}\)Ru and \(^{88}_{38}\)Kr + \(^{92}_{42}\)Mo were used to produce the \(^{179}\)Hg and \(^{177}\)Au nuclei, respectively. Studying the evaporation residues (ER, recoils)-\(\alpha _1\)-\(\alpha _2\) correlations and \(\upalpha \)-\(\gamma \) coincidences, a new \(\upalpha \) decay with E\(_\alpha \) = 6156(10) keV was observed from \(^{179}\)Hg. This decay populates the (9/2\(^-\)) excited state at an excitation energy of 131.3(5) keV in \(^{175}\)Pt. The internal conversion coefficient for the 131.3(5) keV transition de-exciting this state was measured for the first time. Regarding the \(^{177}\)Au nucleus, a new \(\upalpha \) decay with E\(_\alpha \) = 5998(9) keV was observed to populate the 156.1(6) keV excited state in \(^{173}\)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 \(^{173}\)Ir. Properties of the \(^{179}\)Hg and \(^{177}\)Au \(\upalpha \) decays were examined in a framework of reduced widths and hindrance factors. For clarity and simplicity, the spin and parity assignments (e.g. \(J^{\pi }\)) are presented without brackets throughout the text.