A new and transparent method for the analysis of recoil distance Doppler shift data is presented, which we call the differential decay curve method (DDCM). The DDCM can be used for singles as well as for coincidence plunger data and systematic errors can be discovered with it much easier than in the conventional analysis. In addition we propose a modification of the normal plunger which we call the differential plunger. With the differential plunger in principle it is possible to determine lifetimes from quantities measured at only one target to stopper distance. The DDCM was tested with lifetime data for tZ~ and 128Ba.Nuclear Reaction: 11~ 3n)lZ~ E=54.5MeV; recoil Doppler shift; deduced z, enriched targets, Ge detectors

We examine a quantum phase transition in gamma-soft nuclei, where the O(6) limit is simultaneously a dynamical symmetry of the U(6) group of the interacting boson model and a critical point of a prolate-oblate phase transition. This is the only example of phase transitional behavior that can be described analytically for a finite s,d boson system.

The nucleus 94 Mo was investigated using a powerful combination of γ-singles photon scattering experiments and γγ-coincidence studies following the βdecay of 94m Tc. The data survey short-lived J π = 1 + , 2 + states and include branching ratios, E2/M 1 mixing ratios, lifetimes and transition strengths. The proton-neutron mixed-symmetry (MS) 1 + scissors mode and the 2 + MS state are identified from M 1 strengths. A γ transition between MS states was observed and its rate was measured. Nine M 1 and E2 strengths involving MS states agree with the O(6) limit of the Interacting Boson Model-2 using the proton boson E2 charge as the only free parameter.

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 ...

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Lifetimes of states in 150Nd were measured using the recoil distance method following Coulomb excitation of 150Nd by a 132 MeV 32S beam. The experiment was performed at the Yale Tandem accelerator, employing the SPEEDY gamma-ray detector array and the New Yale Plunger Device. Reduced transition probabilities in 150Nd are compared to the predictions of the critical point symmetry X(5) of the phase/shape transition that occurs for the N = 90 rare earth isotones. Very good agreement was observed between the parameter-free (apart from scale) X(5) predictions and the low-spin level scheme of 150Nd, revealing this as the best case thus far for the realization of the X(5) symmetry.

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We identify a Jpi = 3(+)(ms) state in 94Mo. This identification is based on six M1 and E2 strengths and is the first identification of a 3(+)(ms) state from B(M1) and B(E2) values. The transition strengths were determined from the measurement of Doppler shifts, branching ratios, and E2/M1 mixing ratios, obtained from gammagamma directional correlations following the 91Zr(alpha,n) reaction and the beta(+) decay of (94)Tc(m). The interacting boson model agrees with the observations, which prove the 2(+) mixed-symmetry states to be a building block in nuclear structure.