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HK: Physik der Hadronen und Kerne

HK 18: Nuclear and Particle Astrophysics II

HK 18.2: Vortrag

Dienstag, 12. März 2002, 17:15–17:30, C

Measurement of the ¹⁹⁷Au(γ,n)¹⁹⁶Au cross section close above the reaction threshold^* — •P. Mohr, K. Vogt, M. Babilon, W. Bayer, T. Hartmann, C. Hutter, K. Lindenberg, K. Sonnabend, S. Volz, and A. Zilges — Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany

Recently, the interest in (γ,n) reactions has been revived because of their astrophysical relevance for the nucleosynthesis of neutron-deficient p nuclei [1]. It has been shown that the astrophysical (γ,n) reaction rate depends on the (γ,n) cross section only in narrow energy window – a Gamow-like window – above the (γ,n) threshold [1,2]. We have measured (γ,n) reaction rates for several nuclei in a quasi-thermal photon bath at typical temperatures of a supernova explosion [1,3].

The cross section of the reaction ¹⁹⁷Au(γ,n)¹⁹⁶Au has been measured at the S-DALINAC close above the reaction threshold at E_thr = 8.071 MeV using the method of photoactivation. From a combination of our result and data from literature [4] we derive the ¹⁹⁷Au(γ,n)¹⁹⁶Au cross section from threshold to the giant dipole resonance with very small uncertainties. This cross section can be used as standard in future experiments.

[1] P. Mohr et al., Phys. Lett. B 488, 127 (2000).

[2] P. Mohr et al., Nucl. Phys. A688, 82c (2001).

[3] K. Vogt et al., Phys. Rev. C 63, 055802 (2001).

[4] B. L. Berman et al., Phys. Rev. C 36, 1286 (1987); A. Veyssiere et al., Nucl. Phys. A159, 561 (1970); G. M. Gurevich et al., Nucl. Phys. A351, 257 (1981); H. Utsunomiya et al., to be published. ^* supported by DFG (contracts Zi 510/2-1 and FOR 272/2-1).