Alpha-decay of mass-separated gold and platinum isotopes

An α-decay study of mass-separated ^181-186Au isotopes was carried out in order to improve the existing data and also to obtain nuclear structure information of the daughters. The α-decay of platinum isotopes, which were the daughter of the gold isotopes, was also studied. Data were collected utilizing the University Isotopes Separator at Oak Ridge (UNISOR) which is on line to the Holifield Heavy Ion Research Facility (HHIRF) at the Oak Ridge National Laboratory (ORNL). ^181-183Au isotopes were produced by the reaction of ¹⁹F on a C foil (diffused with Yb); ^184-186Au isotopes were produced by the reaction of ¹²C on a stack of tantalum foils with a total thickness of 20 mg/cm². Multiscale spectra of the α-particles, γ-rays, and electrons as well as coincidence spectra of γ – α, γ – γ, and γ-e^- were collected. Energies and half-lives of the α-particles were measured and branching ratios were calculated from the multiscale and singles spectra. The measured α-decay energies were compared to the 1985 mass tables. Fine structures in the α-spectra were observed in the ^181-185Au cases. Alpha-emissions from ¹⁸⁶Au and ¹⁸⁵Pt were observed for the first time. From the energies, half-lifes, and branching ratios of the α-transitions, the hinderance factors for 22 α-transitions from the gold isotopes and 3 α-transitions from the platinum isotopes were calculated. The unhindered α-transition were identified. From the α – γ coincidence data, α-decay schemes of the gold isotopes were constructed. Twelve γ-transitions between 9 levels, 4 γ-transitions between 4 levels, and 6 γ-transitions between 6 levels were observed from the α-decay of ¹⁸¹Au, ¹⁸³Au, and ¹⁸⁴Au, respectively. From the magnitude of the hinderance factors, spins were assigned to some of these levels. A low-lying level in ¹⁸¹Ir populated by one of the α-transitions was identified as being dominated by the unfavored [541] Nilsson orbital.