Z1,2 exciton resonant luminescence in large size CuCl nanocrystallites

Near-resonant conditions upon the highly degenerated (2S) Z1,2-exciton band are used to take advantage of a disorder-induced relaxation of the k-selection rule in order to investigate the unreported direct activation of the (1S) Z1,2 exciton luminescence in large-size CuCl nanocrystallites. Extremely rich spectra display simultaneously the (1S) Z3 and (1S) Z1,2 luminescences. Moreover the unusual antistokes shift between the maxima of the Z1,2 excitonic absorption and emission bands is attributed to an apparent increase in the spatial confinement due to resonance-related density effects. This point supports the key idea of a resonance-based activation of the Z1,2 exciton in the photoluminescence spectra.