| abstract |
A particulate luminescent composition is disclosed that, when excited by electromagnetic radiation at a first frequency, emits electromagnetic radiation at a second frequency equal to or within 1500 cm'1 of the first frequency. The luminescent composition comprises substantially spherical particles having a weight average particle size of less than about 10 μm and a particle size distribution such that at least about 90 weight percent of the particles are not larger than twice the average particle size. |