CdSe, InP, and ZnO colloidal quantum dots of 1.5–2.5 nm radius show <3 meV homogeneous width at 10 K for the midinfrared ${1S}_e{-1P}_e$ intraband transition around 300 meV. A weak temperature dependence leads to a homogeneous width of less than 10 meV at 200 K for 2.3 nm radius CdSe. The strength of the LO-phonon replica is in quantitative agreement with expectations from bulk parameters.

• Received 24 September 2001

DOI:https://doi.org/10.1103/PhysRevB.64.245342