Subbarrier nucleon transfer: Doorway to heavy-ion fusion

Nucleon-transfer cross sections have been measured at subbarrier energies in collisions between Sn target nuclei and light (¹⁶,18O) and heavy (⁵⁸Ni) projectile nuclei. Large differences in cross sections correlate directly with the subbarrier fusion enhancement, suggesting nucleon transfer as an important doorway to fusion with a direct dependence on the overall transfer strengths. Simple two-level mixing considerations support this picture.