Speaker
Description
Charge-exchange isovector collective modes have been studied extensively in the last four decades. The Gamow-Teller (GT) resonance is the most studied because GT transitions, aside from their interest from the nuclear structure point of view, play very important roles in various phenomena in nature [1]. In nucleosynthesis, the $\beta$-decay of nuclei along the s- and r-processes determine the paths that these processes follow and the abundances of the elements synthesized. In supernova collisions, GT transitions are of paramount importance in the pre-supernova phase where electron capture occurs on neutron-rich fp-shell nuclei at the high temperatures of giant stars. Electron capture is mediated by GT transitions. Electron capture removes the electron pressure that keeps the star from collapsing precipitating a cataclysmic implosion followed by a huge explosion throwing much of the star material into space and leaving a neutron star or black hole behind [2,3]. Also, the charge-exchange isovector spin giant monopole resonance (IVSGMR) and isovector spin giant dipole resonance (IVSGDR) have been discovered and have been studied in a few nuclei. Their macroscopic as well as microscopic properties have been determined [4,5]. In this talk, I will concentrate on measurements of GT$^+$ strength via the (d,$^2$He) reaction.
[1] M. N. Harakeh and A. van der Woude, Giant Resonances: Fundamental High-Frequency Modes of Nuclear Excitations (Oxford University Press, New York, 2001).
[2] H. A. Bethe et al., Nucl. Phys. A324, 487 (1979).
[3] G. M. Fuller, W. A. Fowler, M. J. Newman, Astrophys. J. 293, 1 (1985), and references therein.
[4] H. Akimune et al., Phys. Rev. C 52, 604 (1995)
[5] R.G.T. Zegers et al., Phys. Rev. Lett. 90, 202501 (2003).
