Time Resolved Study of Photoluminescence from Se2-Molecule in KI

Properties of optically excited states of the Se 2 - molecule in KI have been studied by the measurement of absorption, luminescence and excitation spectra. From the excitation spectrum, it is confirmed that the 3.6 eV absorption band originates from the same center as the 2.4 eV band and is ascribed to the Se 2 - molecule in KI. Thermal quenching of ordinary luminescence (OL) in KI:Se 2 - and shortening of the OL decay time are interpreted in terms of a thermally activated non-radiative decay process of the excited state 2 ∏ u in the Se 2 - molecule. The weak emission in the energy region higher than the 0 ′ -0 line is confirmed to be “hot luminescence” (HL) by means of the time-resolved spectroscopy. The HL in this system has a decay time less than 50 ps and is detectable not only in the higher energy region of the 0 ′ -0 line but also in the lower energy region.