Potential-Energy and Differential-Stopping-Power Functions from Energy-Loss Spectra of Fast Ions Channeled in Gold Single Crystals

Structure has been observed in the energy-loss spectrum of ions channeled between low-index planes in thin Au single crystals. It is proposed that the cause of this structure lies in the nature of the transverse oscillations of the ion in the interplanar potential. The particle's motion is characterized by an anharmonic oscillation; the wavelength is a function of the amplitude, and each amplitude is characterized by an energy loss. With narrowly collimated beams and small-angle detector, only particles having an integral number of wavelengths within the crystal are detected. Measurement of the wavelengths gives information about the interplanar potential. The dependence of energy loss on amplitude gives a mapping of the stopping power in the channel. Various features of the model are tested and quantitative measurements for 3-MeV ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ ions and 60-MeV ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$ are given. Correlations with atomic parameters are discussed.