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 α-particle spectroscopy. The isotopes were produced by bombarding ²⁴¹Am and ²⁴³Am targets with ¹²C and ¹³C ions accelerated by the Berkeley heavy-ion linear accelerator. The half-lives of the nuclides and the energies of the main α-particle groups, respectively, were observed to be: ²⁴⁸Md: 7 +/- 3 sec, 8.32 +/- 0.02 MeV; ²⁴⁹Md: 24 +/- 4 sec, 8.03 +/- 0.02 MeV; ²⁵⁰Md: 52 +/- 6 sec, 7.75 +/- 0.02 MeV; ²⁵¹Md: 4.0 +/- 0.5 min, 7.55 +/- 0.02 MeV; ²⁵²Md: 2.3 +/- 0.8 min, no α decay. The α-particle energies of ²⁴⁵Es, ²⁴⁶Es, and ²⁴⁷Es, produced mainly by (HI,αxn) 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 ²⁴⁷Es 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. α-decay hindrance factors were calculated using the spin-independent equations of Preston. The α-decay energy systematics of the mendelevium isotopes is discussed.