The results of calculating the energy spectra of protons transmitted and reflected from thin layers of gold are presented. The simulation results are compared with experimental data. It is shown that the stopping measurement results are affected by such factors as the multiple scattering, the geometry of the experiment, and the morphology and roughness of the target. An analysis of the angular dependence for particles passing through a thin film makes it possible to obtain information about the interaction potential between a particle and a solid. The obtained results on the potential agree with the data from experiments on the reflection of particles from the surface of a solid and differ markedly from the data on the potential determined from the scattering of particles in the gas phase. Keywords: energy spectra, angular distribution, interatomic interaction potentials, electronic stopping, straggling.