8-12 July 2013
Investigation of the radiative strength function in 74Ge
Presented by Dr. DINESH NEGI on 9 Jul 2013 from 14:10 to 14:30
Type: Oral Presentation
Track: Track B - Nuclear, Particle and Radiation Physics
The Radiative Strength Function (RSF) represents the ability of nuclear matter to absorb and emit photons. It is one of the input parameters, along with the nuclear level density, for the calculations of nuclear cross sections and reaction rates relevant to astrophysical processes which are invoked to explain the origin of elements heavier than iron . In this work we investigate the dependence of the RSF on the spin and parity of the final state and on the different reactions to excite quasi-continuum states, which are found in the region of high-level density below the particle threshold. This provides not only information about the validity of the Brink hypothesis  but will also help to better understand reactions in astrophysical environments. In this effect, an international collaborative effort is made to study the gamma decay of the quasi-continuum states of 74Ge using different reactions at different experimental facilities in the USA, Europe and South Africa. In this talk I will give an overview of the collaborative experiments and will report on the preliminary results from the 74Ge(4He,4He')74Ge reaction. The experiment was performed at iThemba LABS, with the AFRODITE gamma detector array in conjunction with two particle-telescopes consisting of two silicon detectors each of dimensions 5cm X 5cm. The telescopes were placed at an angle of ±45 degrees with respect to the beam axis. The method  of extracting the RSF consists of detecting correlated particle-gamma-gamma events. By selecting particles of specific energy the entrance excitation energy into the system is determined. A gate on gamma transitions from the discrete states selects the coincidence primary transitions feeding this state. The condition of having the sum of energies of the primary and the discrete gamma-rays equal to the excitation energy then provides unambiguous primary gamma-ray spectra from which the RSF is determined. * This work is based on research supported by the National Research Foundation of South Africa and on work performed under the auspices of the U.S. Department of Energy Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344  A.C. Larsen and S. Goriely, Phys. Rev. C 82,014318 (2010).  D.M. Brink, PhD Thesis, Oxford University (1955).  M.Wiedeking et. al., Phys. Rev. Lett. 108, 162503 (2012).