Fine structure in the  decay of Hg and Au

Area of Science:

• Nuclear Physics
• Nuclear Spectroscopy
• Radioactive Decay

Background:

• Understanding the fine structure of radioactive decays is crucial for nuclear structure models.
• Previous studies on Mercury (Hg) and Gold (Au) isotopes have provided limited information on their decay properties.

Purpose of the Study:

• To investigate the alpha-decay fine structure of Mercury-186 (Hg) and Gold-187 (Au) nuclei.
• To identify new decay paths and transitions in these isotopes.
• To measure nuclear properties such as excitation energies, transition energies, and internal conversion coefficients.

Main Methods:

• Experiments were conducted at the Accelerator Laboratory of the University of Jyväskylä (JYFL), Finland.
• Heavy-ion fusion-evaporation reactions (Kr + Ru and Kr + Mo) were used to produce Hg and Au nuclei.
• Recoil separator RITU and a digital data acquisition system were employed for decay spectroscopy, including evaporation residue (ER)-alpha correlations and alpha-alpha coincidences.

Main Results:

• A new alpha decay with E_alpha = 6156(10) keV was observed from Hg, populating a (9/2) excited state in Platinum-182 (Pt) at 131.3(5) keV.
• The internal conversion coefficient for the 131.3(5) keV transition in Pt was measured for the first time.
• A new alpha decay with E_alpha = 5998(9) keV was observed for Au, populating a 156.1(6) keV excited state in Iridium-183 (Ir). Two de-excitation paths from this state were identified.
• A new 215.7(13) keV transition was observed depopulating a 424.4(13) keV excited state in Ir.
• Properties of the Hg and Au alpha decays were analyzed using reduced widths and hindrance factors.

Conclusions:

• The study successfully identified new alpha decays and transitions in Hg and Au isotopes, significantly enhancing the understanding of their decay properties.
• The measurements provide valuable data for refining nuclear structure models and understanding the mechanisms of radioactive decay in this region of the nuclear chart.
• The newly determined nuclear properties, including excitation energies and internal conversion coefficients, offer critical benchmarks for theoretical calculations.