  We study the low-temperature magneto-photoluminescence (PL) from individual
CdSe nanocrystals. Nanocrystals having a small "bright" exciton fine structure
splitting ($<$0.5 meV) exhibit a conventional left- and right-circularly
polarized Zeeman PL doublet in applied magnetic fields. In contrast,
nanocrystals with large fine structure splitting ($>$1 meV) show an anomalous
magneto-PL polarization, wherein the lower-energy peak becomes circularly
polarized with increasing field, while the higher-energy peak remains linearly
polarized. This unusual behavior arises from strong mixing between the
absorbing and emitting bright exciton levels due to strong anisotropic exchange
interactions.
