Photophysics of polycyclic aromatic hydrocarbons adsorbed on silica gel surfaces. 2. Lifetime distribution and symmetry

In a lifetime distribution analysis of six polycyclic aromatic hydrocarbons (PAHs) adsorbed on silica gel surfaces, a dramatic photophysical effect on the surface can be seen in the PAHs where the lowest excited singlet state is of 1 L b type. This suggests that this effect is related to the symmetry of the lowest excited singlet state of the particular molecule. In addition, a comparison of the photophysical behavior of these PAHs adsorbed on a highly dehydroxylated and on a hydroxylated silica gel surface suggests that the natures of these two types of adsorption may be different. These results show that the regularized lifetime distribution analysis is a useful tool in the surface photophysical studies