Luminescence and allied phenomena
The phenomenon of luminescence with its varied aspects has been a rather old and fascinating field of pure and applied research all over the world. In Indian research laboratories also, investigations on luminescence started quite early in this century.
The luminescent properties are intimately related to the energy levels of the solid, and the different facets of the phenomenon are caused by the multitude of electronic processes that may occur inside the material; structure sensitive properties like luminescence are largely determined by the nature, concentration, spatial distribution and the mutual interactions of the various types of lattice imperfections of the phosphor.
Worthwhile investigations on luminescene and allied phenomena have proceeded mostly along the studies of: (i) the preparation of luminescent materials of commercial and scientific importance, (ii) decay, themoluminescence and energy transfer, (iii) nature of luminescence and related centres, (iv) nonradiative transitions and quantum efficiency, (V) different methods of exciation, (vi) excitons-interatomic and molecular interactions, etc., (vii) transient and relaxation processes, (viii) high intensity excitation and non-linear effects, (ix) external perturbation effects, and (x) electronic properties like photoconducting, photoelectric, photodielectric, photomagnetic properties, etc.
Inestigations on luminescence and allied phenomena have undergone dramatic changes in quality and quantity in the course of the last few decades. The inherent scientific and commercial importance of the subject is indicated by the phenomenal growth of literature in this field. Such a tremendous rate of growth has, obviously, been inspired by numerous factors like: (1) growth of fluorescent lamps and related industry, (2) advent of cathode ray tubes, TV screens and infra-red detection devices, (3) detection of ionising particles and radiations-demand for scintillators, (4) preparation of materials of `luminescence grade' purity. advances in semiconductor devices and related electronics and computer, (5) advent of lasers, and (6) advances made in theory and experimental techniques.
The trends of progress made in research on some aspects of luminescence and allied phenomena are briefly indicated in this paper. It can be easily seen that advances in this field have influenced tremendously the growth of science and technology during the past fifty years all over the world.
Indian Journal of History of Science, Vol. 27, no. 4 (1992).