Computed pseudo-2D RPES maps for different choices of the angle ﹩{\vartheta }_{\mathrm{HHC}}﹩ (defined in the main text). The left column refers to ﹩{{\rm{H}}}^{-}+{\mathrm{HC}}_{2}{\rm{H}}﹩ for ﹩\vartheta ={135}^{{\rm{o}}}﹩ (above) and ﹩\vartheta ={90}^{{\rm{o}}}﹩ (below) whereas the same results for the ﹩{{\rm{H}}}^{-}+{\mathrm{HC}}_{4}{\rm{H}}﹩ system are in the right columns. The profiles of the corresponding MEP energy behaviors are also shown by different colors in all four panels of the present figure.