Jahn–Teller effects and surface interactions in multiply-charged fullerene anions and the effect on scanning tunneling microscopy images

Abstract

We investigate the combined effects of Jahn–Teller (JT) coupling and interactions with a surface substrate on fullerene anions C602- to C604-. JT coupling alone causes the C60 ions to instantaneously distort from the icosahedral symmetry of the neutral molecule to a lower symmetry, with the molecule moving dynamically between a set of equivalent distortions. When adsorbed on a surface, the number of equivalent minimum-energy distortions is reduced. The implications of this on observed scanning tunneling microscopy (STM) images will be discussed, and comparisons made with existing experimental data. We show that a consistent interpretation of the images from all of the charge states of C60 can only be obtained using a JT model in which the symmetry is further reduced by surface interactions. The comparison with experimental data also allows us to determine relationships between the quadratic Jahn–Teller coupling and surface interaction parameters.