K-shell capture by protons from O2, N2, and Ne

We have measured the ratio of the cross section for K-electron capture to that for total K-vacancy production for 0.75--5-MeV protons on targets of O2, N2, and Ne. This was done by detecting Auger electrons from the target K-shell relaxation in coincidence with charge-neutralized projectiles. The fraction of K-shell vacancy production due to electron capture ranges from 0.028% to 3.3%, and the K-shell fraction of total electron capture from 2.5% to over 80%. By combining these data with previously measured (or calculated) cross sections for total K-vacancy production, we deduce cross sections for K-shell capture alone. The cross sections follow Oppenheimer-Brinkman-Kramers scaling laws for higher velocities, and are in fair absolute agreement with more complete charge-transfer calculations