OBSERVATION AND CALCULATION OF INTERNAL STRUCTURE IN SCANNING-TUNNELING-MICROSCOPY IMAGES OF RELATED MOLECULES

The scanning tunneling microscope has been used to distinguish among a series of related molecules on Pt(111) by details of their observed s tructures. The electronic isomers naphthalene and azulene can be recog nized, as can three structural isomers of monomethylazulene, as well a s dimethyl- and trimethylazulene. The number and position of substitue nts affect the diffusion rates, sticking coefficients, and orientation s. A simple methodology based on extended Huckel theory, including the substrate, generates electron and hole density plots which show very good agreement with the data.