Molecular effect in the formation of the energy spectrum upon the transmission of low-energy hydrogen ions through ultrathin carbon foils

The energy spectra of ions transmitted through ultrathin diamond-like foils irradiated by H$^+$, H$^+_2$, and H$^+_3$ ions with energies from 2 to 12 keV/nucleon are studied. For molecular ions incident on the target with identical velocities, a considerable broadening of the energy spectrum is observed with an increase in the ion mass. The spectrum halfwidth reduced to the identical particle velocity remains constant for each type of incident ion, irrespective of the foil thickness.