Evolution of shell structure in neutron-rich calcium isotopes

We employ interactions from chiral effective field theory and compute the binding energies and low-lying excitations of calcium isotopes with the coupled-cluster method. Effects of three-nucleon forces are included phenomenologically as in-medium two-nucleon interactions, and the coupling to the particle continuum is taken into account using a Berggren basis. The computed ground-state energies and the low-lying 2+ states for the isotopes 42,48,50,52Ca are in good agreement with data, and we predict the excitation energy of the first 2+ state in 54Ca at 1.9 MeV, displaying only a weak sub-shell closure. In the odd-mass nuclei 53,55,61Ca we find that the positive parity states deviate strongly from the naive shell model.Comment: 5 pages, 4 figures; small correction of effective 3NF and slight change of the corresponding parameters; updated figures and tables; main results and conclusions unchange

Microactuators based on ion-implanted dielectric Electroactive Polymer Membranes (EAP)

We report on the first ion-implanted dielectric electroactive polymer actuator that was successfully microfabricated and tested. Ion implantation is used to make the surface of the polymer locally conducting. Implanting the compliant electrodes solves the problem of how to microfabricate patterned electrodes having elasticity close to that of the insulating elastomer. Dieletric EAP actuators combine in an exceptional way high energy-density, while allowing large amplitude displacements [1,2]. The ion-implant approach avoids the deposition of metal electrodes on the polymer, normally accompanied with an undesired stiffening of the membrane. The actuator consists of a 35-um thick ion implanted PDMS membrane bonded to a silicon chip containing a hole. We observed 110-um vertical displacements of a square membrane measuring 1 mm2. ©2005 IEEE

Excitation energies of superdeformed states in 196Pb: towards a systematic study of the second well in Pb isotopes

The excitation energy of the lowest-energy superdeformed band in 196Pb is established using the techniques of time-correlated γ-ray spectroscopy. Together with previous measurements on 192Pb and 194Pb, this result allows superdeformed excitation energies, binding energies, and two-proton and two-neutron separation energies to be studied systematically, providing stringent tests for current nuclear models. The results are examined for evidence of a “superdeformed shell gap.

Excitation energies of superdeformed states in Pb-196: towards a systematic study of the second well in Pb isotopes

The excitation energy of the lowest-energy superdeformed band in Pb-196 is established using the techniques of time-correlated gamma-ray spectroscopy. Together with previous measurements on Pb-192 and Pb-194, this result allows superdeformed excitation energies, binding energies, and two-proton and two-neutron separation energies to be studied systematically, providing stringent tests for current nuclear models. The results are examined for evidence of a "superdeformed shell gap.

Magnetic properties of the \mth{\nu j_{15/2}} intruder orbital in the superdeformed minimum of \chem{^{197}Pb}

This work has established eight cross-talk transitions between the two signature partner superdeformed (SD) bands in $^{197}$Pb with the EUROBALL IV spectrometer. Directional correlations from oriented states measurements confirm the $\Delta I = 1$ character of these transitions. The flat behaviour of the dynamical moment of inertia and the agreement between the experimental and microscopic HF+BCS values of $\left( g_K-g_R\right) K/Q_0$ suggest that the configuration of the SD bands is based upon the $\nu [752]5/2^-$ neutron intruder orbital. The derived effective spin gyromagnetic factor $g_s^{\rm eff}$ is found to be not quenched, and is close to the theoretical $g_s^{\rm free}$ value