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HK: Physik der Hadronen und Kerne

HK 18: Nuclear and Particle Astrophysics II

HK 18.4: Vortrag

Dienstag, 12. März 2002, 17:45–18:00, C

Determination of the (n,γ) reaction rate of unstable ¹⁸⁵W in the astrophysical s-process via its inverse reaction — •K. Sonnabend, P. Mohr, K. Vogt, M. Babilon, W. Bayer, D. Galaviz, T. Hartmann, C. Hutter, S. Volz, and A. Zilges — Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany

The β-unstable isotope ¹⁸⁵W is a branching point in the astrophysical s-process. Therefore the ratio of the (n,γ) reaction rate and β-decay rate of ¹⁸⁵W is of common interest. We have measured the inverse reaction ¹⁸⁶W(γ,n)¹⁸⁵W due to the experimental difficulties in measuring the (n,γ) reaction rate of an unstable isotope directly. Our preliminary result is in agreement with theoretical predictions for the (γ,n) cross section [1] and available data [2-4]. Therefore, the predicted (n,γ) cross section under s-process conditions of about 700 millibarn and the derived neutron density [5] are confirmed.
^* supported by the DFG (contracts Zi510/2-1 and FOR272/2-1)

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[2] B.L. Berman et al., Phys. Rev. 185, 1576 (1969)

[3] A.M. Goryachev, G.N. Zalesnyĭ, IZV. An. KazSSR 6, 8 (1978)

[4] G.M. Gurevich et al., Nucl. Phys. A351, 257 (1981)

[5] F. Käppeler et al., ApJ. 366, 605 (1991)