A new technique is proposed for analysis of the composition of incident hydrogen ion beams accelerated by Van de Graaff electrostatic accelerators. The procedure is based on the analysis of the energy distribution of the neutral fraction of the hydrogen ion beam by a silicon surface barrier detector. It is shown that along with the main beam components (H+, H0) at the energy E0, another component exists at the energy 0.25 E0. This component is brought about through acceleration and breakup of molecular H2+ ions. However such inhomogeneities do not play a noticeable role in formation of the low energy tail of hydrogen ions backscattered from thin self-supporting films.