Direct Evidence of Breakdown of Spin Statistics in Ion-Atom Charge Exchange Collisions

Recent experimental studies have questioned the validity of spin statistics assumptions, particularly in charge exchange processes occurring in atomic MeV collisions. Here, we study spin-resolved single electron capture processes in collisions between ${\mathrm{C}}^{3+}$ ions and helium within an energy range of $1.25--400\text{ }\mathrm{keV}/\mathrm{u}$. Using high resolution reaction microscope and multielectronic theoretical approaches, we directly measure and calculate the true population information of the ${\mathrm{C}}^{2+}(1{s}^{2}2s2p\text{ }^{1,3}P)$ states at the time of electron capture, overcoming the previous experimental and theoretical difficulties. At the level of integral and scattering angle differential cross sections, our results demonstrate the breakdown of pure spin statistics arguments, especially at high impact energies where they are traditionally expected to be valid. These novel findings and conclusions raise intriguing questions both in the understanding of the electronic dynamics during such fast collisional processes and in exploring quantum manipulation of atomic and molecular reactivity.