Eur. Phys. J. A (2025) 61: 43
https://doi.org/10.1140/epja/s10050-025-01513-9

Regular Article - Experimental Physics

Fine structure in the $\mathrm{\alpha }$ decay of $_{}^{179}$Hg and $_{}^{177}$Au

¹ Heavy Ion Laboratory, University of Warsaw, Ludwika Pasteura 5A, 05-077, Warsaw, Poland
² Institute of Physics, Slovak Academy of Sciences, 84511, Bratislava, Slovakia
³ Oliver Lodge Laboratory, University of Liverpool, L69 7ZE, Liverpool, UK
⁴ Department of Physics, College of Science Education, University of Sulaimani, 334, Sulaimani, Kurdistan Region, Iraq
⁵ School of Physics, Engineering and Technology, University of York, YO10 5DD, Heslington, UK
⁶ Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai-mura, 319-1195, Naka-gun, Ibaraki, Japan
⁷ Accelerator Laboratory, Department of Physics, University of Jyväskylä, 40014, Jyväskylä, Finland
⁸ INFN Laboratori Nazionali di Legnaro, 35020, Padova, Italy
⁹ iThemba Laboratory for Accelerator Based Sciences, P.O. Box 722, 7129, Somerset West, South Africa
¹⁰ Department of Physics and Astronomy, University of the Western Cape, 7535, Bellville, South Africa
¹¹ School of Computing, Engineering and Physical Sciences, University of the West of Scotland, PA1 2BE, Paisley, UK
¹² Department of Physics, Faculty of Science, Ege University, 35100, Izmir, Turkey
¹³ Department of Physics, Faculty of Science and Arts, Sakarya University, 54187, Sakarya, Turkey
¹⁴ Physics Division, Argonne National Laboratory, 60439, Lemont, USA
¹⁵ Institute of Experimental and Applied Physics, Czech Technical University, Prague, Czech Republic
¹⁶ Laboratory of Radio-Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, 00014, Helsinki, Finland
¹⁷ CERN, 1211, Geneva 23, Switzerland
¹⁸ School of Computing, Engineering and Physical Sciences, University of the West of Scotland, PA1 2BE, Paisley, UK
¹⁹ STFC Daresbury Laboratory, WA4 4AD, Daresbury, Warrington, UK
²⁰ Helsinki Institute of Physics, P.O. Box 64, 00014, Helsinki, Finland
²¹ STUK - Radiation and Nuclear Safety Authority, P.O. BOX 14, 00811, Helsinki, Finland
²² Physics Division, Argonne National Laboratory, 60439, Argonne, IL, USA

^a andrej.herzan@savba.sk

Received: 21 November 2024
Accepted: 11 February 2025
Published online: 7 March 2025

Abstract

The $\mathrm{\alpha }$-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 ⁸²₃₆Kr + ¹⁰⁰₄₄Ru and ⁸⁸₃₈Kr + ⁹²₄₂Mo were used to produce the ¹⁷⁹Hg and ¹⁷⁷Au nuclei, respectively. Studying the evaporation residues (ER, recoils)-${\alpha }_1$-${\alpha }_2$ correlations and $\mathrm{\alpha }$-$\gamma$ coincidences, a new $\mathrm{\alpha }$ 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 $\mathrm{\alpha }$ 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 $\mathrm{\alpha }$ 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.