The weak 4? -* it transition in ,s O was observed with a branching ratio (0.30 ±0.08)%, using the 14 C(a,/) ls O radiative-capture reaction at E a = \A4 MeV. The corresponding B(E2'Ai -* 2 3 + ) =5.7 ± 1.9 Weisskopf units appears noncollective, and serves as a crucial test of microscopic models predicting collective band structures and enhanced E\ decays in ls O; it is smaller by a factor of 3-8 than predictions of such models, and cannot be reproduced by the well-established coexistence model for ls O, suggesting that our understanding of collective motion in light nuclei is incomplete. We review recent suggestions for extending coexistence models.

The Tandem Van de Graaff at Brookhaven National Laboratory has delivered pulsed gold beam to the Alternating Gradient Synchrotron (AGS) and AGS Booster since 1992 for relativistic heavy ion physics. There is an ongoing effort to improve the quality and intensity of the negative ion beam delivered to the Tandem from the present Cs sputter sources. Because the beam energy is low (approximately 30 keV) and the current high, there are significant losses due to space charge forces. One of the ways being explored to overcome these losses is to neutralize the space charge forces with ionized background gas. On an ion source test bench, using three different gases (Ar, N2, and Xe), the percentage of current transported from the source to a downstream Faraday cup was increased from 10% to 40% by bleeding in gas. Bleeding in Xe resulted in the best transmission. The time dependence of the neutralization as a function of gas pressure was also observed. This system is presently being transferred to the Negative Ion Injector of the Tandem for use in upcoming heavy ion experiments.

The energy and relative intensities of L-MM Auger lines show that for low-MeV Kr -Kr collisions most of the ionization takes place during the collision, due to the prompt emission of as many as 12 electrons per atom. The later decay of L-shell vacancies contributes in only a minor way to the final ionization state. These results provide insights into a variety of collision phenomena, including shifts in Auger and x-ray energies, fluorescence yields, and equilibrium charge distributions in high-Z foils.

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