Dependence of Spontaneous Emission Lifetime Upon Surrounding Dielectric Medium

Einstein demonstrated in 1917 that spontaneous emission always occurs for matter in excited states from a consideration of the thermal equilibrium between the matter and the radiation field. It was not until 1946 that Purcell noticed that the spontaneous emission decay time, such a fundamental property of matter, is not always constant for a given system, but can depend strongly on the environment. A lot of theoretical work has been carried out since 1970 to study the modification of spontaneous emission decay time of luminescent centers in various environments. The fundamental problem of the modification of spontaneous emission decay time of isolated luminescent ions due to the surrounding media is still not solved, although most publications have long been using an "accepted" solution.Experiments will be performed in this project with special care to conform to model conditions. The spontaneous emission lifetimes of selected ions will be measured as a function of the media in which they are embedded. The results will be compared with modeling predictions so that an understanding of the appropriate model to a particular situation can be developed.The spontaneous emission rate is an important parameter for luminescent materials. Although there are copious published results on this parameter, there are very few systematic studies of the dependence of the spontaneous emission rate upon the refractive index.