A phenomenological theory of infra-red sensitive phosphors is given which assumes the existence of two types of luminescent centers in order to account for the so-called “inertia” effects in the rise of brightness. The equations describing the electron transfer processes have been integrated and show under certain conditions a very rapid initial rise in brightness followed by a relatively slow attainment of the maximum. The effect of varying the intensity of the stimulating infra-red radiation is discussed.
ROBERT C. HERMAN and CHARLES F. MEYER, "The Rise in Brightness of Infra-Red Sensitive Phosphors," J. Opt. Soc. Am. 39, 729-730 (1949)