SIZE-SELECTIVE 2-PHOTON SPECTROSCOPY OF CUCL SPHERICAL QUANTUM DOTS

We analyze luminescence spectra resulting from a resonant size-selecti ve two-photon excitation of the low-energy confined Z(3)-exciton state s in CuCl spherical nanocrystals. Excitation spectra,of the two-photon -excited luminescence (TPL) bands and size dependences of band energie s show that the TPL bands arise due to annihilation of the exciton in the lowest-energy state excited both directly and through the higher-e nergy confined states. It is shown that the oserved features of the TP L fine structure can be unambiguously interpreted in terms of longitud inal (L) and transverse (T) confined exciton states and resonant enhan cement of phonon-assisted luminescence when the energy gap between IS and 1P states of the T exciton is close to the LO-phonon energy.