ABSTRACT

This chapter provides the food analyst with an introduction to the principles of luminescence spectroscopy. An attempt has been made to keep the level of the treatment commensurate with the needs of the investigator. Luminescence is the consequence of electronic transitions between energy levels. In molecules, these energy levels correspond to various molecular states. Any process that leads to a diminished emission is called quenching. A quenching mechanism usually involves another molecule called a quencher and is merely another means by which an excited singlet or triplet state can lose energy without emitting light. High concentrations of solute molecules may lead to aggregation in which there is an enhancement of the phosphorescence and a quenching of the fluorescence. This situation reflects the formation of ex-citon bands which result as a consequence of the transition dipoles of individual molecules being close enough to interact leading to delocalization of the excitation energy.