Picosecond lifetimes in 46 V and 46 Ti were determined using the recoil distance Doppler-shift technique with a plunger device coupled to a setup of five HP Ge detectors enhanced by one EUROBALL CLUSTER detector. The experiment was carried out using the 32 S( 16 O,pn) reaction at 38 MeV at the Cologne FN TANDEM facility. The differential decay curve method in coincidence mode was employed to derive lifetimes for five excited states in each nucleus. The resulting E2 transition probabilities are compared with existing shell model calculations and a comparison within the Tϭ1 isospin triplet is given. Absolute E1 strengths of the 2 Ϫ decay in 46 V are discussed.The investigation of NϭZ nuclei is an exciting topic in nuclear structure physics, to which a lot of experimental and theoretical work has been devoted recently. Self-conjugate nuclei are symmetric with respect to the isospin degree of freedom and allow a sensitive testing of the isospin symmetry. This symmetry leads to selection rules, e.g., E1 transitions between low lying states with Tϭ0 character are strictly forbidden. The only way to enhance E1 strengths between such states is to assume an admixture of Tϭ1 components of the wave function, caused by the Coulomb interaction or by isospin violating parts of the strong interaction.The determination of isospin mixing matrix elements via lifetime measurements is of special interest in odd-odd N ϭZ nuclei with valence particles in the f 7/2 shell. In 46 V, much interesting data have been accumulated recently ͓1-6͔. A very peculiar finding was the isospin forbidden 2 Ϫ →1 ϩ transition with a relative E1 strength six times stronger than the strength of a competing allowed one with ⌬Tϭ1 ͓1͔. In order to achieve a better comparison between allowed and forbidden E1 transitions, it is important to determine ͑more and͒ absolute transition probabilities in this nucleus. The present work reports on the decay properties of the 2 1 Ϫ ,T ϭ0 state and explains the observed relative E1 strengths.Aside from this, a comparison with 46 Ti, the isobaric analog partner of 46 V, is presented. In the Tϭ1 triplet the reduced E2 matrix elements have a linear dependence upon T z , which follows from general arguments based on the ideas of isospin symmetry ͓7͔, provided that isospin is a good quantum number. Precise B(E2;2 1 ϩ →0 ϩ ) values provide a stringent test to this theoretical relation. The new data are in better agreement with the theoretical description than a previous value.In 46 V recent model calculations in the full p f shell without any truncation for the positive parity states describe the experimental level order and branching ratios well ͓1͔. Nevertheless, reliable data on transition probabilities are necessary for an overall comparison of experimental data with shell model calculations. Despite its relevance such information is still scarce.We performed a recoil distance Doppler-shift ͑RDDS͒ experiment with the Köln coincidence plunger device ͓8͔ at the FN TANDEM facility at the University of Cologne. Excited states ...

Lifetimes of prolate intruder states in 186Pb and oblate intruder states in 194Po have been determined by employing, for the first time, the recoil-decay tagging technique in recoil distance Doppler-shift lifetime measurements. In addition, lifetime measurements of prolate states in 188Pb up to the 8+ state were carried out using the recoil-gating method. The B(E2) values have been deduced from which deformation parameters |beta2|=0.29(5) and |beta2|=0.17(3) for the prolate and the oblate bands, respectively, have been extracted. The results also shed new light on the mixing between different shapes.

We present an ab initio study of the electronic stopping power of protons in copper over a wide range of proton velocities v = 0.02 − 10 a.u. where we take into account non-linear effects. Timedependent density functional theory coupled with molecular dynamics is used to study electronic excitations produced by energetic protons. A plane-wave pseudopotential scheme is employed to solve the time-dependent Kohn-Sham equations for a moving ion in a periodic crystal. The electronic excitations and the band structure determine the stopping power of the material and alter the interatomic forces for both channeling and off-channeling trajectories. Our off-channeling results are in quantitative agreement with experiments, and at low velocity they unveil a crossover region of superlinear velocity dependence (with a power of ∼ 1.5) in the velocity range v = 0.07 − 0.3 a.u., which we associate to the copper crystalline electronic band structure. The results are rationalized by simple band models connecting two separate regimes. We find that the limit of electronic stopping v → 0 is not as simple as phenomenological models suggest and it plagued by band-structure effects.

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Following the heavy-ion fusion-evaporation reaction 32S+24Mg at 95 MeV beam energy the lifetimes of analogue states in the T(z)=+/-1/2 A=51 mirror nuclei 51Fe and 51Mn have been measured using the Cologne plunger device coupled to the GASP gamma-ray spectrometer. The deduced B(E2;27/2(-)-->23/2(-)) values afford a unique opportunity to probe isoscalar and isovector polarization charges and to derive effective proton and neutron charges, epsilon(p) and epsilon(n), in the fp shell. A comparison between the experimental results and several different large-scale shell-model calculations yields epsilon(p) approximately 1.15e and epsilon(n) approximately 0.80e.