PROBING PRE-FORMED ALPHA PARTICLES IN THE GROUND STATE OF NUCLEI

In this Rapid Communication, we report on {alpha}-particle emission through the nuclear breakup in the reaction {sup 40}Ca on a {sup 40}Ca target at 50 A MeV. It is observed that, similar to nucleons, {alpha} particles can be emitted to the continuum with very specific angular distribution during the reaction. The {alpha}-particle properties seem to be compatible with an {alpha} cluster in the daughter nucleus that is perturbed and is emitted by the short-range nuclear attraction of the collision partner. A time-dependent theory that describes the {alpha}-particle wave-function evolution is able to qualitatively reproduce the observed angular distribution. This mechanism offers new possibilities for studying {alpha}-particle properties in the nuclear medium.