In-beam spectroscopy with intense ion beams: Evidence for a rotational structure in 246Fm

The rotational structure of 246Fm has been investigated using in-beam γ -ray spectroscopic techniques. The experiment was performed using the JUROGAMII germanium detector array coupled to the gas-filled recoil ion transport unit (RITU) and the gamma recoil electron alpha tagging (GREAT) focal plane detection system. Nuclei of 246Fm were produced using a 186 MeV beam of 40Ar impinging on a 208Pb target. The JUROGAMII array was fully instrumented with Tracking Numerical Treatment 2 Dubna (TNT2D) digital acquisition cards. The use of digital electronics and a rotating target allowed for unprecedented beam intensities of up to 71 particle-nanoamperes for prompt γ -ray spectroscopy at a level of approximately 11 nb. With all these major experimental advances a rotational band is observed in 246Fm.peerReviewe

Investigation of high-K states in 252No

In this paper we investigate the rotational band built upon a two-quasiparticle 8− isomeric state of 252No up to spin I π = 22−. The excited states of the band were populated with the 206Pb(48Ca, 2n) fusion-evaporation reaction. An unambiguous assignment of the structure of the 8− isomer as a 7/2+[624]ν ⊗ 9/2−[734]ν configuration has been made on the basis of purely experimental data. Comparisons with triaxial self-consistent Hartree-FockBogoliubov calculations using the D1S force and breaking time-reversal as well as z-signature symmetries are performed. These predictions are in agreement with present measurements. Mean-field calculations extended to similar states in 250Fm support the interpretation of the same two-neutron quasiparticle structure as the bandhead in both N = 150 isotones.peerReviewe

First prompt in-beam gamma-ray spectroscopy of a superheavy element: the 256Rf

Using state-of-the-art γ-ray spectroscopic techniques, the first rotational band of a superheavy element, extending up to a spin of 20 ¯h, was discovered in the nucleus 256Rf. To perform such an experiment at the limits of the present instrumentation, several developments were needed. The most important of these developments was of an intense isotopically enriched 50Ti beam using the MIVOC method. The experimental set-up and subsequent analysis allowed the 256Rf ground-state band to be revealed. The rotational properties of the band are discussed and compared with neighboring transfermium nuclei through the study of their moments of inertia. These data suggest that there is no evidence of a significant deformed shell gap at Z = 104.peerReviewe

Shell-Structure and Pairing Interaction in Superheavy Nuclei: Rotational Properties of the Z=104 Nucleus 256Rf

The rotational band structure of the Z ¼ 104 nucleus 256Rf has been observed up to a tentative spin of 20@ using state-of-the-art -ray spectroscopic techniques. This represents the first such measurement in a superheavy nucleus whose stability is entirely derived from the shell-correction energy. The observed rotational properties are compared to those of neighboring nuclei and it is shown that the kinematic and dynamic moments of inertia are sensitive to the underlying single-particle shell structure and the specific location of high-j orbitals. The moments of inertia therefore provide a sensitive test of shell structure and pairing in superheavy nuclei which is essential to ensure the validity of contemporary nuclear models in this mass region. The data obtained show that there is no deformed shell gap at Z ¼ 104, which is predicted in a number of current self-consistent mean-field models.peerReviewe