Heavy-ion reactions as spin probes

Heavy-ion reactions can be powerful probes for spin-transfer strength in nuclei, provided their reaction mechanism is simple so that a correlation can be established between cross sections and the relevant matrix elements. We discuss the desirable features of heavy-ion reactions in general and a series of tests of reaction mechanisms that have been carried out for two of the most favorable reactions; (6Li, 6He) and (12C, 12N). We establish that the (6Li, 6He) reaction is one-step in nature above 25 MeV∙nucleon−1 and establish a calibration function relating cross sections and Gamow–Teller matrix elements. We also find that the (12C, 12N) reaction is likely to be dominated by the one-step process above about 50 MeV∙nucleon−1.