Study of spin polarization of residual nuclei in heavy ion reactions by γ-ray circular polarization measurement

It is well known that fast fast light particles are emitted strongly at the foward direction in heavy ion reactions. To study the reaction mechanism of the phenomena, we measured circular polarization of coincident γ-rays emitted from the residual nucleus and deduced spin polarization. The experiments were performed using 7Li and 14N beams from RIKEN cyclotron. The spin polarization for (7Li, α) reaction depends on α-particle energy and can be well explained as a recoil effect in the trition transfer process. The spin polarization for the (14N, α) reaction, that also depends on α-particle energy, can be explained as a competition of massive-transfer process and deep-inelastic process. (author)