The simultaneous exposure of a photographic emulsion to naphthalene and Xe ions, i.e. polyat. and monoat. ions of the same nominal mass, demonstrated a 250% higher emulsion response to the naphthalene mol. ion than to Xe+. Also, the more compact naphthalene mol. ion tended to give a darker image on the emulsion than the more conformationally mobile n-nonane ion. However, the emulsion response was essentially the same for the naphthalene and quinoline ions, which have similar shape and size.