A systematic investigation of the yrast superdeformed (SD) rotational bands in even-even nuclei of the A ∼ 190 mass region has been performed within the framework of the cranked relativistic Hartree-Bogoliubov theory. The particle-hole channel of this theory is treated fully relativistically, while a finite range two-body force of Gogny type is used in the particle-particle (pairing) channel. Using the well established parameter sets NL1 for the Lagrangian and D1S for the Gogny force, very good description of experimental data is obtained with no adjustable parameters.Despite the fact that superdeformation at high spin has been studied experimentally and theoretically for one and half decade a number of theoretical questions such as, for example, the underlying mechanism of identical bands and the role of pairing correlations in the regime of weak pairing in rotating nuclei, remains still not fully resolved and further development of theoretical tools is definitely required. During the last decade the relativistic mean field (RMF) theory 1 became a standard microscopic tool of nuclear structure studies. Systematic investigation of SD rotating nuclei in the regime of weak pairing correlations in the A ∼ 150 2,3,4,5 and A ∼ 60 (see Ref.6 and references therein) mass regions revealed that cranked relativistic mean field (CRMF) theory 7,3 , in which pairing correlations are neglected, provides an astonishingly accurate description of the properties of SD bands, such as moments of inertia, transition quadrupole moments Q t , effective alignments i ef f , singleparticle properties at superdeformation etc. In particular we have to keep in mind that this theory has only seven free parameters fitted to the properties of few spherical nuclei 8 . One should clearly recognize that the neglect of pairing correlations used in CRMF theory is an approximation because pairing correlations being weak are still present even at the highest rotational frequencies. Moreover, the rotational properties of nuclei at low and medium spin are strongly affected by pairing correlations. In order to describe such properties within the relativistic framework, cranked relativistic Hartree-Bogoliubov theory has been developed 9,10,11 . This theory is an extension of CRMF theory to the description of pair- ing correlations in the rotating frame. In this theory the particle-hole channel is treated fully relativistically on the Hartree level, while the particle-particle channel is approximated by the best currently available non-relativistic interaction: the pairing part of the Gogny force. The use of this force has a clear advantage since it provides both an automatic cutoff of high-momentum components and, as follows from non-relativistic studies, an excellent description of pairing properties in finite nuclei. An additional feature of CRHB theory is that approximate particle number projection is performed by means of the Lipkin-Nogami method (further APNP(LN)) 12,13,14 . The comparative study of pairing and rotational properties in the rare eart...

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We have identified two isomers in 254No, built on two- and four-quasiparticle excitations, with quantum numbers K pi = 8- and (14+), as well as a low-energy 2-quasiparticle Kpi = 3+ state. The occurrence of isomers establishes that K is a good quantum number and therefore that the nucleus has an axial prolate shape. The 2-quasiparticle states probe the energies of the proton levels that govern the stability of superheavy nuclei, test 2-quasiparticle energies from theory, and thereby check their predictions of magic gaps.

We report the first observation of the 108 Xe → 104 Te → 100 Sn α-decay chain. The α emitters, 108 Xe [Eα = 4.4(2) MeV, T1 /2 = 58 +106 −23 µs] and 104 Te [Eα = 4.9(2) MeV, T1 /2 <18 ns], decaying into doubly magic 100 Sn were produced using a fusion-evaporation reaction 54 Fe(58 Ni,4n) 108 Xe, and identified with a recoil mass separator and an implantation-decay correlation technique. This is the first time α radioactivity has been observed to a heavy self-conjugate nucleus. A previous benchmark for study of this fundamental decay mode has been the decay of 212 Po into doubly magic 208 Pb. Enhanced proton-neutron interactions in the N = Z parent nuclei may result in superallowed α decays with reduced α-decay widths significantly greater than that for 212 Po. From the decay chain, we deduce that the α-reduced width for 108 Xe or 104 Te is more than a factor of 5 larger than that for 212 Po.