Interplay between Quantum Shells and Orientation in Quasifission

The quasifission mechanism hinders fusion in heavy systems through breakup within zeptoseconds into two fragments with partial mass equilibration. Its dependence on the structure of both the collision partners and the final fragments is a key question. Our original approach is to combine an experimental measurement of the fragments' mass-angle correlations in Ca-40 + U-238 with microscopic quantum calculations. We demonstrate an unexpected interplay between the orientation of the prolate deformed U-238 with quantum shell effects in the fragments. In particular, calculations show that only collisions with the tip of U-238 produce quasifission fragments in the magic Z = 82 region, while collisions with the side are the only ones that may result in fusion.