Infrared photofragmentation (panel a, black trace) and reference precursor (gray trace, shifted up 0.2 amu) mass spectra, and IRMPD spectrum (panels b–f, black trace) for protonated, perdeuterated phenanthrene – [H − C₁₄D₁₀]⁺. Panels b–f further contain calculated spectra (blue) for five different position isomers, for which the structures are shown on the left. The theoretical IR spectra were calculated using B3LYP/6-311++G(2d,p) and the ground-state energies in M06-2X/6-311++G(2d,p).