Long-Lived Luminescence in Anthracene Crystals Excited by Both β Ray and Visible Light

Abstract

A new luminescence component was observed when anthracene crystals were excited by visible light under β-ray irradiation. It originates from the light-excitation of some excited state generated by β-ray irradiation. Though the spectrum agrees with that of fluorescence and the lifetime is about 7 ms, it is not the normal delayed fluorescence resulting from triplet-triplet annihilation. A remarkable difference from the luminescence which has ever been observed is the existence of a threshold in the intensity of excitation light.