ABSTRACT
Luminescence is the phenomenon of emission of electromagnetic radiation by a substance, in excess of thermal radiation (i.e., for a cause other than a rise in its temperature), taking place instantaneously or over an extended period of time, after it has been excited outwardly by some form of energy such as
light, electric eld, electron beam, nuclear radiations, chemical energy, heat, or mechanical energy. It is thus the emission of light produced by a means other than heat energy.
