Correlation of Ionization Probabilities with Geometric Charge Cross Sections

The previous study of the ionization probabilities has been extended to include additional high molecular weight unsubstituted polynuclear aromatic hydrocarbons. The charge distributions for these ions were calculated using Huckel molecular orbitals. These charge distributions were used to calculate a geometric charge cross section by an impact parameter approach assuming a simple classical collision model. The geometric charge cross sections were found to correlate with the molecular ionization probabilities for the unsubstituted compounds, suggesting that the relative ionization probabilities for these compounds result from purely geometric considerations.The polymethylbenzene series was studied to determine whether the marked effect of substituent groups is purely geometric or whether additional group effects exist. It was found that a 3.3‐fold greater group efficiency of methyl groups relative to the ring carbon atoms was necessary to correlate with these data. A number of nitrogen heterocyclics were ...