Optical transitions in semiconductor nanostructures

Employing the Maxwell equations and conventional boundary conditions for the radiation field on the nanostructure interfaces, we compute the radiative spontaneous decay rate of optical transitions in spherical semiconductor nanocrystals, core–shell nanocrystals and nanostructures comprising more than one shell. We also show that the coupling between optical transitions localized in the shell of core–shell nanocrystals and radiation field is determined by both conventional electro-multipole momenta and electro-multipole “inverse” momenta. The latter are proportional to the core radius even for interband transitions that should result in very strong optical transitions.