S. McDaniel

Enhanced quadrupole collectivity at N = 40: the case of neutron-rich Fe isotopes.

The transition rates for the 2_{1}^{+} states in 62,64,66Fe were studied using the Recoil Distance Doppler-Shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N=40. The results are interpreted by the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N=40 as governed by the number of valence protons with respect to Z~30. The deformation suggested by the experimental data is reproduced by state-of-the-art shell calculations with a new effective interaction developed for the fpgd valence space.

Mechanisms in Knockout Reactions

We report the first detailed study of the relative importance of the stripping and diffraction mechanisms involved in nucleon knockout reactions, by the use of a coincidence measurement of the residue and fast proton following one-proton knockout reactions. The measurements used the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results for the reactions 9Be(9C,8B+X)Y and 9Be(8B,7Be+X)Y are presented and compared with theoretical predictions for the two reaction mechanisms calculated using the eikonal model. The data show a clear distinction between the stripping and diffraction mechanisms and the measured relative proportions are very well reproduced by the reaction theory. This agreement adds support to the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes.

Quadrupole collectivity beyond N = 28: intermediate-energy Coulomb excitation of (47,48)Ar.

We report on the first experimental study of quadrupole collectivity in the very neutron-rich nuclei (47,48)Ar using intermediate-energy Coulomb excitation. These nuclei are located along the path from doubly magic Ca to collective S and Si isotopes, a critical region of shell evolution and structural change. The deduced B(E2) transition strengths are confronted with large-scale shell-model calculations in the sdpf shell using the state-of-the-art SDPF-Uand EPQQM effective interactions. The comparison between experiment and theory indicates that a shell-model description of Ar isotopes around N=28 remains a challenge.

Observation of mutually enhanced collectivity in self-conjugate 3876Sr 38

The lifetimes of the first 2

Collectivity atN=50:Ge82andSe84

^{+}

Collectivity at N=50: Ge-82 and Se-84

states in the neutron-deficient

In-beam gamma-ray spectroscopy of very neutron-rich nuclei: excited states in 46S and 48Ar.

^{76,78}

In-beam γ-ray spectroscopy at the proton dripline: 23Al

Sr isotopes were measured using a unique combination of the

Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

\gamma

Mirror Energy Differences at Large Isospin Studied through Direct Two-Nucleon Knockout

-ray line-shape method and two-step nucleon exchange reactions at intermediate energies. The transition rates for the 2