Hadronic cosmic rays of energies below about 100 MeV nucleon-1 are thought to be an important component of the Galactic ecosystem. However, since these particles cannot be detected near Earth due to the solar modulation effect, their composition and flux in the interstellar medium are very uncertain. Atomic interactions of low-energy cosmic rays with interstellar gas can produce a characteristic nonthermal X-ray emission comprising very broad lines from de-excitations in fast ions following charge exchange. We suggest that broad lines at ˜0.57 and ˜0.65 keV could be detected from a dark molecular cloud in the local interstellar medium. These lines would be produced by fast oxygen ions of kinetic energies around 1 MeV nucleon-1.