Measurements of r-process nuclei

Progress in the astrophysical understanding of r-process nucleosynthesis also depends on the knowledge of nuclear-physics quantities of extremely neutron-rich isotopes. In this context, experiments at CERN-ISOLDE have played a pioneering role in exploring new shell-structure far from stability. Possible implications of new nuclear-data input on the reproduction of r-abundance observations are presented.Comment: 10 pages, 3 figures; Proc. "Nuclei in the Cosmos 2000", Nucl. Phys.

Stellar and nuclear-physics constraints on two r-process components in the early Galaxy

Proceedings of "Nuclei in the Cosmos 2000", Aarhus, DanmarkComment: 3 pages, 2 figures; to be publ. in Nucl. Phys.

An evaluation of the efficacy of a social skills training program with young multiply handicapped students

This study was designed to analyze the efficacy of a formal social skills training (SST) program on a group of self-contained, multiply handicapped students. The treatment group, consisting of 24 students, underwent five months of formal SST, at least three times a week for a 30 to 50 minute period. The participating teachers were trained in, and followed, Elias and Clabby\u27s Social Decision Making and Problem Solving: Revised Readiness Curriculum (1988). They were asked to complete pre- and post test Likert scales (Social Problem Solving Skills Checklist) on the presence of specific social skills in each student. Average gains in the areas of self control skills, group and social awareness, and getting along with self and others were calculated, totaled, and analyzed against three comparison groups representing a Regular Education sample (22 students), a Resource Center sample (17 students), and a Self Contained, Multiply Handicapped comparison sample (21 students). Results indicated that formal SST not only improved the acquisition of specific skills, but enabled the Self-Contained Treatment group to obtain the highest percentage gains in all areas, progressing at a faster rate than any of the comparison groups. This study emphasized the importance of a SST program, and it\u27s efficacy on young, multiply handicapped students

Nuclear Structure Studies at ISOLDE and their Impact on the Astrophysical r-Process

The focus of the present review is the production of the heaviest elements in nature via the r-process. A correct understanding and modeling requires the knowledge of nuclear properties far from stability and a detailed prescription of the astrophysical environment. Experiments at CERN/ISOLDE have played a pioneering role in exploring the characteristics of nuclear structure in terms of masses and beta-decay properties. Initial examinations paid attention to far unstable nuclei with magic neutron numbers related to r-process peaks, while present activities are centered on the evolution of shell effects with the distance from the valley of stability. We first show in site-independent applications the effect of both types of nuclear properties on r-process abundances. Then, we explore the results of calculations related to two different `realistic' astrophysical sites, (i) the supernova neutrino wind and (ii) neutron star mergers. We close with a list of remaining theoretical and experimental challenges needed to overcome for a full understanding of the nature of the r-process, and the role CERN/ISOLDE can play in this process.Comment: LATEX, 38 pages, 16 figures, submitted to Hyperfine Interaction

A tentative 4- isomeric state in Sr-98

Annual Report 2001, Institut fuer Kernchemie, Johannes-Gutenberg-Universitaet, Mainz, GermanyComment: 3 pages, 1 figur

Charged-Particle and Neutron-Capture Processes in the High-Entropy Wind of Core-Collapse Supernovae

The astrophysical site of the r-process is still uncertain, and a full exploration of the systematics of this process in terms of its dependence on nuclear properties from stability to the neutron drip-line within realistic stellar environments has still to be undertaken. Sufficiently high neutron to seed ratios can only be obtained either in very neutron-rich low-entropy environments or moderately neutron-rich high-entropy environments, related to neutron star mergers (or jets of neutron star matter) and the high-entropy wind of core-collapse supernova explosions. As chemical evolution models seem to disfavor neutron star mergers, we focus here on high-entropy environments characterized by entropy $S$, electron abundance $Y_e$ and expansion velocity $V_{exp}$. We investigate the termination point of charged-particle reactions, and we define a maximum entropy $S_{final}$ for a given $V_{exp}$ and $Y_e$, beyond which the seed production of heavy elements fails due to the very small matter density. We then investigate whether an r-process subsequent to the charged-particle freeze-out can in principle be understood on the basis of the classical approach, which assumes a chemical equilibrium between neutron captures and photodisintegrations, possibly followed by a $\beta$-flow equilibrium. In particular, we illustrate how long such a chemical equilibrium approximation holds, how the freeze-out from such conditions affects the abundance pattern, and which role the late capture of neutrons originating from $\beta$-delayed neutron emission can play.Comment: 52 pages, 31 figure