Measurement of Charge-Transfer Cross Sections for 0.25- to 2.5-MeV Protons and Hydrogen Atoms Incident upon Hydrogen and Helium Gases

Measurements of the single- and double-electron-capture cross section for protons, ${\sigma }_{10}$ and ${\sigma }_{1,-1}$, respectively, and the single-electron-loss cross section for hydrogen atoms ${\sigma }_{01}$ within the energy range 0.25 to 2.5 MeV for molecular-hydrogen and atomic-helium target gases have been made by the method of observing the rate of growth with target-gas number density of the fast-collision products from an originally pure primary beam. The present values of ${\sigma }_{10}$ and ${\sigma }_{01}$ agree within 10% with the data of Barnett and Reynolds below 1 MeV and confirm the extrapolation of their data which passes through the single measurements of ${\sigma }_{10}$ and ${\sigma }_{01}$ for 12.9- and 21-MeV deuterons and 20-MeV deuterium atoms by Berkner, except for ${\sigma }_{10}$ in He where the extrapolation of the present data passes below the values of Berkner. The experimental values of ${\sigma }_{01}$ agree with calculated values of ${\sigma }_{01}$ derived from the Born and free-collision approximations within the experimental uncertainty of ±10%. The values of ${\sigma }_{1,-1}$ in molecular hydrogen decrease from 5.1×${10}^{-25\mathrm{}}$ ${\mathrm{cm}}^2$/molecule at 0.4 MeV to 1.6×${10}^{-28\mathrm{}}$ ${\mathrm{cm}}^2$/molecule at 1 MeV with an experimental uncertainty of up to 60%. These values are lower than the first-Born-approximation calculations by Mittleman.