Pyroluminescence

The last luminescent phenomenon is pyroluminescence. It is the emission of light from molecules or atoms that were previously excited by heating to high temperatures, for example by a flame.

The classical examples include salts of alkali metals and alkali earth metals in the flame of Bunsen burner. The temperature of Bunsen burner is sufficient for thermal excitation of sodium, potassium, lithium or calcium atoms.

Another very attractive experiment is burning of trimethyl borate. During this process, an excited intermediate is produced (BO*) which emits a characteristic green light.

 

IMG_0412_maly IMG_0414_maly

Fig. 8: Trimethyl borate flame with a characteristic colour