الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Luminescence is the emission of light from any substance, and occurs from electronically excited
states. Luminescence is formally divided into two categories—fluorescence and
phosphorescence—depending on the nature of the excited state. In excited singlet states, the
electron in the excited orbital is paired (by opposite spin) to the second electron in the ground-
state orbital. Consequently, return to the ground state is spin allowed and occurs rapidly by
emission of a photon. The emission
rates of fluorescence are typically108 s–1, so that a typical
fluorescence lifetime is near 10 ns (10.0 x 10–9 s).
Photoluminescence is a type of optical spectroscopy in which a molecule is promoted to an
electronically excited state by absorption of ultraviolet, visible, or near infrared radiation. The
emitted light is detected. Photoluminescence processes are subdivided into fluorescence and
phosphorescence [Wehry E. L., 1993]. The key characteristic of fluorescence spectrometry is its
high sensitivity.