Abstract
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•Jahn–Teller effects in fullerene anions adsorbed on surfaces are investigated.•Published scanning tunneling microscopy images of fullerene anions are interpreted.•Images from all charge states are interpreted using a consistent Jahn–Teller model.•Surface, Jahn–Teller and Coulomb interactions must all be taken into account.•Information of the strength of quadratic Jahn–Teller couplings is obtained.
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.