Observation of the 1P excitonic states in Cd(S,Se)-glass quantum dots.

The 1S to 1P excitonic transition in Cd(S,Se) quantum dots in glass was observed as a distinct peak in an infrared absorption spectrum (2-5 μm) induced with a subpicosecond visible laser pulse (585 nm). The temporal behavior of the induced absorption at the peak indicates that the 1P to 1S exciton relaxation is faster than 0.7 ps and the 1S exciton lifetime is about 20 ps. The 1S to 1P transition energy allows us to determine the eigenenergies for both electron and holes as well as the effective mean radius of dots. Direct transmission electron microscopy examination independently confirms the sizes of the quantum dots