Magnetic circular dichroism studies of charge-transfer-to-solvent spectra

Abstract

The magnetic circular dichroism spectra of the charge-transfer-to-solvent (ctts) transitions of bromide and iodide ions in acetonitrile have been measured and analysed. These results support the assumed spherical symmetry of the solvent orbital and, for the bromide system, they demonstrate that the excited state has the expected angular momentum. For the iodide, however, an angular momentum some 30 % larger than expected is found which may indicate that higher-lying ctts states involve solvent orbitals having d- rather than s-type symmetry.

The energy separation of the two ctts band maxima for each ion are found to be well reproduced by the diffuse model of the excited state, or by a model in which the excited electron is imagined to be confined to a cage of solvent molecules surrounding the ion. The confined and Rydberg orbital models appear to be at variance with experiment in this respect.