Brook's discovery of the unusual spectral properties of a-silyl ketones stimulated research to determine the mechanism of silicon'seffe~ t.~,~ A shift to lower energy in an n+ s* transition can be produced either by lowering the energy of the excited s* state or by raising the energy of the ground state. Theoretical molecular orbital models indicate that the s* state could be stabilized by interaction with the empty d orbitals on~ ilicon.~ J The energy level ...
