Alpha-Decay Properties of Some Lutetium and Hafnium Isotopes Near the 82-Neutron Closed Shell

The 84- and 85-neutron isotopes of lutetium, ${\mathrm{Lu}}^{155}$ and ${\mathrm{Lu}}^{156}$, and the 85- and 86-neutron isotopes of hafnium, ${\mathrm{Hf}}^{157}$ and ${\mathrm{Hf}}^{158}$, were produced by bombarding a ${\mathrm{Sm}}^{144}$ target with high-energy ${\mathrm{F}}^{19}$ and ${\mathrm{Ne}}^{20}$ ions. These nuclides decay primarily by alpha-particle emission. Alpha-decay energies and half-lives were measured. An alpha-emitting isomeric state was observed for ${\mathrm{Lu}}^{156}$. The alpha reduced widths of these nuclides are close to those observed for other isotones in this region. A search was made for proton-decay branches but none was observed. Some results of a ${\mathrm{Sm}}^{144}$+${\mathrm{S}}^{32}$ bombardment are presented, and speculations are made with regard to the future production of the ultra-neutron-deficient 84- to 86-neutron isotopes above hafnium.