Electron Capture by 40-, 155-, and 600-MeV Protons in Thin Foils of Mylar, Al, Ni, and Ta

The charge-exchange process has been studied at much higher energies than previously examined. Equilibrium charge distributions have been measured in foils of Mylar, Al, Ni, and Ta for protons of 155 and 600 MeV, and deuterons of 80 MeV. Estimates have been made for the loss cross sections ${\sigma }_l$, and the resulting capture cross sections ${\sigma }_c$ are compared with theoretical expectations. Up to 155 MeV, ${\sigma }_c$ can be reasonably well accounted for by the nonradiative capture process. Above this energy there are significant departures from this simple behavior which are consistent with the predicted onset of radiative capture. However, because of possible relativistic effects, such an interpretation is not certain. The present data suggest several interesting areas for future theoretical and experimental study.