Product Yields from Multiphoton Processes in Cyclohexane and Solutions of Aromatic Compounds

Article abstract of DOI:10.1021/j100089a030

Products from the 248 nm photolysis of neat cyclohexane are measured as a function of light intensity and total exposure.The yields of these products increase in proportion to the square of the incident intensity, indicating a biophotonic process, and the quantum yields are independent of the total incident light.The quantum yields (per two photons absorbed) are 0.6 +/- 0.1, 0.6 +/- 0.1 and 0.04 +/- 0.01, for H2, cyclohexene, and bicyclohexyl, respectively.These quantum yields indicate that molecular decomposition (to H2 and cyclohexene) of excited cyclohexane resulting from the geminate recombination of electron-solvent radical cation pairs created in the biphotonic ionization process accounts for more than 80percent of the ions.For a given incident light intensity, the addition of an aromatic solute (anthracene, biphenyl, or acenapthene) causes the amount of these products observed to increase, despite the fact that the light absorption by the solvent is markedly less.This indicates the occurence of processes by which energy absorbed by an aromatic molecule results in decomposition of the cyclohexane.Evidence that this process is proton transfer from excited aromatic radical cations is discussed.