Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.

and due to Auger-type e–h interactions, may still significantly affect holedynamics, particularly in the final stage of hole relaxation between finestructure,band-edge states.However, despite being significantly slower than at high spectralenergies, hole dynamics in the final stage of relaxation between ‘‘absorbing’’and ‘‘emitting’’ states still remain on the sub-pisosecond timescale. Even forvery small NQDs (R = 1.2 nm) for which the splitting of band-edge excitonstates is particularly large, the ‘‘absorbing’’ transition shows a 700-fs decaythat is complementary to the growth of the PL at the position of the‘‘emitting’’ transition (Fig. 8).Ultrafast population dynamics experimentally observed for both thelowest (i.e., ‘‘emitting’’) electron and hole quantized states indicate that despitethe wide separation of electronic states, energy relaxation in stronglyFigure 8 Complementary PL dynamics detected at the positions of the ‘‘absorbing’’(solid circles) and ‘‘emitting’’ (open squares) transitions for 1.2-nm CdSe NQDs fit toa single- and a double-exponential function, respectively (dotted line is a pump-pulseautocorrelation).Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.