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HK: Fachverband Hadronen und Kerne
HK 60: Nuclear Astrophysics
HK 60.7: Talk
Wednesday, March 18, 2009, 18:30–18:45, H-ZO 60
Properties of the first 1/2+ state in 9Be from electron scattering and astrophysical implications* — •Oleksiy Burda, Peter von Neumann-Cosel, and Achim Richter — Institut für Kernphysik, Technische Universität Darmstadt, Germany
The low-energy level structure of the 9Be nucleus has long been a matter of interest, in particular with respect to the strength of three-body α + α + n cluster configurations. This nucleus has the lowest neutron threshold (Sn = 1.6654 MeV) of all stable nuclei. Already the first excited Jπ = 1/2+ state lies at an excitation energy of several tens of keV above the 8Be + n threshold. Parameters of this resonance are of great astrophysical importance since it is believed to provide an important route for the production of carbon and subsequently heavier nuclei triggering the r-process in core-collapse supernovae. Due to its closeness to the neutron threshold the resonance has a strongly asymmetric line shape but despite a large number of different experiments there still exist discrepancies between the various deduced resonance parameters [1]. We present high-resolution inelastic electron scattering experiments on 9Be performed at the S-DALINAC. The resonance parameters of the first excited 1/2+ state in 9Be are derived in a one-level R-matrix approximation from the present and older (e,e′) data [2]. The astrophysically relevant α(α n,γ)9Be reaction rate is extracted and discussed.
[1] F. C. Barker, Aust. J. Phys. 53 (2000) 247.
[2] G. Kuechler et al., Z. Phys. A 326 (1987) 447.
*Supported by the DFG through SFB 634.