Polycyclic aromatic hydrocarbons mass spectra

Pitches consist mostly of fused ring, polycyclic aromatic hydrocarbons with a broad mass spectrum and a molecular mass of 200 to 800 [3] [14]. Since the corresponding molecules are not large enough, they interact only weakly with one another. Most untreated pitches are therefore isotropic. 

Example The EC mass spectrum of benzo[a]pyrene, C20H12, shows the negative molecular ion exclusively at m/z 252 (Fig. 7.14). This spectrum is representative for EC spectra of polycyclic aromatic hydrocarbons (PAHs) [87,88]. One particular PAH, fluoranthene, has recently received much attention as its ion serves as electron donating reactant ion in electron transfer dissociation (ETD, Chap. 9.15). 

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