[en] A theoretical model of energy transfer between Si nanocrystals and Er³⁺ ions in SiO₂ matrix is presented. The mechanism, based on the Coulomb interaction between carriers confined in nanocrystal and f-electrons of erbium ions, is considered to be responsible for the excitation and quenching of the 1.55 μm luminescence, and particularly for its recently discovered nanosecond dynamics. It has been shown that phonon-assisted intraband transition of a confined carrier can give rise to erbium transition into the first excited state with characteristic time being in the nanosecond range