Charge-exchange reactions

The (p,n) charge-exchange reaction can be used to excite Gamow-Teller (GT) and spin-dipole resonances by utilizing a liquid hydrogen target and measuring the slow neutrons with plastic scintillators surrounding the target. Studies of the GT strength are beside their importance in nuclear structure of particular astrophysical interest. Electron-capture reactions leading to stellar collapse and supernova formation are mediated by GT transitions. Basic understanding of all these processes requires reliable knowledge of the GT strength distribution in a large excitation energy range as well as in nuclei far off stability. Cross sections of the spin-dipole giant resonance excited in (p,n) reactions are rather directly related to the neutron-skin thickness. Corresponding measurements were performed so far only for stable isotopes [1]. With exotic nuclear beams, such measurements require secondary beam intensities of the order of 1000 ions/s, and thus a systematic study of neutron skins will be feasible by a method alternative to that consisting of a combination of proton and electron scattering data.

[1] A. Krasznahorkay et al., Phys. Rev. Lett. 82 (1999) 3216.