Download or read book Luminescence Related Phenomena and their Applications written by Hardev Singh Virk and published by Trans Tech Publications Ltd. This book was released on 2013-12-13 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume is indexed by Thomson Reuters BCI (WoS). This special volume consists of eight chapters consisting of seven Review papers and one Research paper. “Luminescence Phenomena: An Introduction” is the first Chapter contributed by KVR Murthy and HS Virk. It explains the basic phenomenon of Luminescence: “Luminescence is "cold light", light from other sources of energy which can take place at normal and lower temperatures. The word luminescence was first used by a German physicist, Eilhardt Wiedemann, in 1888. In Latin ‘Lumen’ means ‘light’. The materials exhibiting this phenomenon are known as ‘Luminescent materials’ or ‘Phosphors’ meaning ‘light bearer’ in Greek. Luminescence is basically a phenomenon of emission of light from an insulator followed by prior absorption of energy from ionizing radiations like, X-rays, alpha, beta and gamma radiations. The energy lifts the atoms of the material into an excited state, and then, because excited states are unstable, the material undergoes another transition, back to its unexcited ground state, and the absorbed energy is liberated in the form of either light or heat or both. The excitation involves only the outermost electrons orbiting around the nuclei of the atoms. Luminescence efficiency depends on the degree of transformation of excitation energy into light, and there are relatively few materials that have sufficient luminescence efficiency to be of practical value”.