Spectroscopic studies beyond the N=152 neutron gap: Decay of Md-255(101) and Md-256(101) - art. no. 044301

The isotopes Md-255 and Md-256 were produced by the irradiation of Es-253 w ith 35-45 MeV alpha particles by (alpha,n) and (alpha,2n) reactions and wer e removed from the target by a helium jet system, alpha, gamma, and alpha-g amma coincidence spectra were measured with Si and Ge(Li) detectors. From t he EC decays of Md-255 and Md-256, levels in Fm-255 and Fm-256 were deduced . Favored alpha decay of Md-255 was found to populate the 7/2(-)[514] singl e-particle state in Es-251, thus establishing the 7/2(-)[514] as the Md-255 ground state. Several gamma rays were observed in the Md-256 alpha-gamma c oincidence spectrum. Fm-256 is the heaviest nucleus in which excited intrin sic states have been identified.