STUDENT AWARD FINALIST: Projectile Coherence Effects in Single and Dissociative Electron Capture in Collision of Protons with H$_{2}$ and He

Recently, we have observed that interference effects, similar to optical Young double-slit interference, in the projectile scattering angle dependent ionization cross sections of H$_{2}$ by 75 k$e$V proton impact are present or not depending on the projectile coherence. This suggests that atomic scattering cross sections in general are sensitive to the projectile coherence, an aspect which has been overlooked for decades. To investigate this effect further, we have measured differential cross sections for single and dissociative capture for 75 and 25 k$e$V protons colliding with H$_{2}$ and He. A significant sensitivity of the cross sections to the projectile coherence was confirmed. For 25 k$e$V we found that interference due to different impact parameters leading to the same scattering angle dominates over molecular two-center interference. This important observation sets the stage for resolving heatedly debated discrepancies between theory and experiment for ionization of He by 100 MeV/amu C$^{6+}$ impact.