The circular dichroism (CD) spectra of the (9R,10R,21R,22R)-9,10,21,22-tetramethyl-9,10,21,22-tetrahydro-7H,12H,19H,24H -dinaphtho [1.8-f,g:1 .8 -o,p] tetraoxacyclooctadecin molecule is studied in terms of a dimer model which includes the interstate mixing of the chromophore (naphthalene) electronic states. The experimental CD spectrum corresponding to the 1 L a state of naphthalene shows a strong solvent effect when going from isooctane solvent to acetonitrile solvent. This effect is studied and explained as a result of changes in the interstate mixing effect.