Fluorescence emission intensity:

The fluorescence emission intensity is decreased through a number of processes such as self quenching, self absorption or inner filter effects and through the presence of external species. This is known as fluorescence quenching. The fraction of the excited molecules in which relax by the fluorescence pathway i.e., through emission of radiation is quantified in terms of a parameter called quantum efficiency or quantum yield.

All fluorescence instruments use fundamentally the similar components as are used in absorption spectrophotometers; therefore, the geometric arrangement of the components is somewhat different. Within luminescence measurement the emitted radiation is measured through the detector at a right angle to the transmitted beam while in case of absorption spectrometers the transmitted radiation is measured along the direction of the incident light. The primary set up of the instrumentation for phosphorescence is same to that of fluorescence. Thus, the sampling technique and the recording procedure required to be modified.

The applications of fluorescence spectroscopy are spread across the disciplines of physical and life sciences and it is becoming a broadly used spectroscopic technique within the fields of Clinical Chemistry, Biochemistry and Molecular Biophysics. The phosphorescence measurements instead are not as general because of the requirements of cryogenic temperatures yet it searches a number of applications in the areas such as pharmaceutical analysis, forensic science, environmental science and analysis of pesticides.