Question

What effect does temperature have on the quantum yields of fluorescence and phosphorescence

Answer 1

The quantum yield or quantum efficiency is used to measure the probability that a molecule will fluoresce or phosphoresce. Fluorescence and phosphorescence are the ratio of the number of the molecules that luminescent to the total number of excited molecules. For highly fluoresce molecules, the quantum efficiency approaches to 1.

Quantum efficiency of Fluorescence decreases with increase in temperature. As the temperature increases, the frequency of the collision increases which increases the probability of deactivation by external conversion. Fluorescence of a molecule decreases when its solvent contains heavy atoms. Orbital spin interaction result from an increase in the rate of triplet formation, which decreases the possibility of fluorescence. Heavy atoms are usually incorporated into solvent to enhance phosphorescence.