Anomalous stopping of protons jointly moving in the material

Titanium layers with thickness ranging from 0.7 to 2.1 µm thick were investigated using the Rutherford backscattering method with protons and molecular hydrogen ions at energies from 0.8 to 1.6 MeV. The layers were deposited by magnetron sputtering onto polished single-crystal silicon substrates. A difference between the Rutherford backscattering spectra obtained with 0.8 MeV protons and 1.6 MeV molecular hydrogen ions was observed. As a possible explanation for this difference, a reduction in the stopping power of the material during the simultaneous passage of two protons was considered. Models based on spherical and Gaussian representations of the electron – phonon excitation region were tested for calculations. The models enabled the computation of the target's stopping power and the dimensions of the regions responsible for energy absorption. Corrections to the conventional procedure for fitting Rutherford backscattering spectra were introduced based on these models. Good agreement between the calculated results and experimental data was achieved. The proposed corrections may be crucial for range calculations of light molecular ions in the design of precision technological processes. The models employed can provide additional insights into the nature of the interaction between light ions and the electron – phonon system of the material.