Münster 2002 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 18: Nuclear and Particle Astrophysics II
HK 18.1: Gruppenbericht
Dienstag, 12. März 2002, 16:45–17:15, C
Nuclear Input Data for the r-Process: Cosmochronometer for Old Halo Stars — •B. Pfeiffer1, K.-L. Kratz1, H. Schatz2, and J.J. Cowan3 — 1Inst. f. Kernchemie, Univ. Mainz — 2NSCL, Michigan State Univ., East Lansing, USA — 3Dep. of Phys. and Astr., Univ. Oklahoma, Norman, USA
The description of the rapid neutron-capture process (r-process) requires environments with a high neutron density, where neutron captures are faster than β-decays, even for unstable nuclei up to 15 - 30 units from stability near the neutron drip-line. These exotic nuclei with a large neutron excess are of considerable interest not only for astrophysics but for nuclear structure studies. They experience dramatic changes giving rise to new shell structures characterized by vanishing gaps [1].
The updated nuclear physics input is applied for classical r-process models. The calculated abundances are compared to new observations of extremely metal-poor, old stars in the Galactic halo. The observed abundances for heavier neutron-capture elements (including the third r-process peak elements) are consistent wth a scaled solar system distribution. Our theoretical production value for Th/U ratio combined with the new observations make more reliable chronometric age estimates possible [2]. These ages are lower limits for the age of the Universe.
[1] B. Pfeiffer et al., Nucl. Phys. A693, 282 (2001)
[2] R. Cayrel et al., Nature 409, 691 (2001); J.J. Cowan et al., submitted to Ap. J.