Collisional Atomic Physics with Molecular Projectiles

Many collisional atomic physics processes are altered when solid targets are bombarded by molecular, compared to atomic, projectiles. We present energy and angular distribution measurements of exiting particles when 50-300 keV H+2 and HeH+ molecules are incident on thin (1.8-5 ¿g/cm2) solid carbon targets. We find that the ratio of molecular to atomic projectile energy loss is velocity and transit time dependent, and ranges from ~ 0.8 to 1.3. The energy distribution of the exiting charged, neutral, and molecular particles are compared and found to be consistent with the assumption that protons of a velocity ¿ v0 do not have bound states while moving in solids.