Studies of Mendelevium Isotopes with Mass Numbers 248 Through 252

Five isotopes of mendelevium, with mass numbers 248 through 252, were studied by means of $\alpha$-particle spectroscopy. The isotopes were produced by bombarding ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ and ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}$ targets with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ ions accelerated by the Berkeley heavy-ion linear accelerator. The half-lives of the nuclides and the energies of the main $\alpha$-particle groups, respectively, were observed to be: ${}_{}{}^{248}{}_{}{}^{}\mathrm{Md}$: 7 ± 3 sec, 8.32 ± 0.02 MeV; ${}_{}{}^{249}{}_{}{}^{}\mathrm{Md}$: 24 ± 4 sec, 8.03 ± 0.02 MeV; ${}_{}{}^{250}{}_{}{}^{}\mathrm{Md}$: 52 ± 6 sec, 7.75 ± 0.02 MeV; ${}_{}{}^{251}{}_{}{}^{}\mathrm{Md}$: 4.0 ± 0.5 min, 7.55 ± 0.02 MeV; ${}_{}{}^{252}{}_{}{}^{}\mathrm{Md}$: 2.3 ± 0.8 min, no $\alpha$ decay. The $\alpha$-particle energies of ${}_{}{}^{245}{}_{}{}^{}\mathrm{Es}$, ${}_{}{}^{246}{}_{}{}^{}\mathrm{Es}$, and ${}_{}{}^{247}{}_{}{}^{}\mathrm{Es}$, produced mainly by ($\mathrm{HI},\alpha \mathrm{xn}$) reactions, were measured to be 7.73 ± 0.02, 7.36 ± 0.03, and 7.31 ± 0.03 MeV, respectively, and the half-life of ${}_{}{}^{247}{}_{}{}^{}\mathrm{Es}$ was found to be 4.7±0.3 min. Excitation curves for producing the Md isotopes and some other activities are presented. Estimates for the electron-capture branching of the Md isotopes are given. $\alpha$-decay hindrance factors were calculated using the spin-independent equations of Preston. The $\alpha$-decay energy systematics of the mendelevium isotopes is discussed.