Köln 2004 – scientific programme

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PV: Plenarvorträge

PV XIX

PV XIX: Plenary Talk

Thursday, March 11, 2004, 11:00–11:30, P

Astrophysics related nuclear structure studies — •Heinrich Johannes Wörtche — Kernfysisch Versneller Instituut

We have exploited transfer reactions in inverse kinematics of type p(^AN, t) ^A−2N in order to populate excited states in unstable nuclei and measure the branching ratios of successive decay modes of astrophysical importance. Up to now, we have investigated the ¹⁵O(α, γ)¹⁹Ne reaction, which is a potential candidate for the breakout from the hot CNO cycles, and the ²¹Na(p, γ)²²Mg reaction, which is related to the temperature-dependent production yield of ²²Na via ²²Mg β⁺-decay in novae environments. The experiments have been performed with ²¹Ne and ²⁴Mg beams provided by the AGOR cyclotron at 43 MeV/u and 55 MeV/u, respectively. Due to the kinematic forward focusing, the tritons as well as the heavy fragments are detected in the large acceptance Big-Bite Spectrometer with 100% geometric efficiency. Our data set a stringent limit on the α-decay branching of relevant states in ¹⁹Ne and yielded spin and parity assignments for excited states in ²¹Na. Relating to neutrino induced reactions, I will present data on the tensor-analyzing powers of the ¹²C(d^→, ²He)¹²B charge-exchange reaction. The measurements were performed with purely tensor-polarized deuteron beams at 172 MeV incident energy. We have studied the sensitivity of the analyzing powers to the excitation of Δ S=Δ L = 1 spin-dipole transitions. I will present results which allow location of the strength up to the nuclear continuum and discuss extension of the measurements in the nuclear mass range relevant for the neutrino detection and neutrino-nuclear processing.