Steric effect of methyl, methoxy, and ethyl substituents on the excimer formation of naphthalene on Al2O3(0 0 0 1)

Structural relaxation of molecules on surfaces can be monitored by observing the spectral evolution as increasing amount of thermal energy is made available. Naphthalene forms excimers in the excited state when amorphously prepared, but relaxes to a more ordered state when heated. Substituent groups on the naphthalene can substantially alter the available pathways during the thermally induced structural relaxation, and is reflected in the formation of excimer or trap fluorescence. A general correlation was determined for the naphthalene substitution with methyl, methoxy, and ethyl groups on the 1- and 2-positions with the pathway taken by the molecular adlayer.