We report direct spectroscopic evidence for parity-forbidden electroni
c transitions in CdSe nanocrystals and relate it through perturbation
theory to an internal electric field. This field is consistent with an
estimated spontaneous polarization of P-s = -0.6 mu C/cm(2) for CdSe.
The observed mixing of odd and even band edge hole states by this sym
metry breaking internal electric field indicates that current theories
of nanocrystal electronic structure, which assume inversion symmetry,
require substantial revision. (C) 1997 American Institute of Physics.