Binding energy determination in a π-stacked aromatic cluster: the anisole dimer

The binding energies of the neutral and positively charged anisole dimer have been determined in molecular beam-laser spectroscopy experiments. This is the first report on the direct experimental determination of the binding energy for an aromatic cluster in π stacked configuration. The anisole dimer is formed by two anisole molecules superimposed in a planar arrangement and it has been proposed as a model system in which the π-stacking interaction, among other intermolecular forces, plays a relevant role. Its binding energy has been determined thanks to both velocity mapping ion/electron imaging experiments and previous spectroscopic information. The binding energy amounts to 3926(250) cm(-1) in the ground state and 4144(250) cm(-1) in the S2 (first spectroscopically accessible) electronic excited state; its value for the positively charged dimer ion increases to 6147(250) cm(-1). These values are quite higher with respect to the results of previous DFT calculations.