S1-T2 LEVEL INVERSION OF 9,10-DIMETHYLANTHRACENE CAUSED BY THE COORDINATION OF ONE RARE-GAS ATOM

Fluorescence lifetimes were measured for isolated 9,10-dimethylanthracene and its van der Waals complexes with rare-gas atoms in supersonic free jets. On the basis of the microscopic solvation effect on S1-T2 intersystem crossing, it is demonstrated that the energy of the S1 electronic origin is located above that of the T2 electronic origin for the isolated molecule and that the relative position of these states is inverted upon coordination with one atom of Ar, Kr or Xe. A similar phenomenon is suggested for the complexation of 9,10-dibromoanthracene with a Xe atom.