The Luminescence of Diamonds

Studies of the luminescence characteristics of different types of industrial diamonds (80-100 mesh dust) have been made. Blue fluorescent diamonds (3,650 A. exciting radiation) exhibit thermoluminescence characteristics of two groups of metastable electronic states, with mean activation energies of 0.5 and 0.7 ev. respectively. Transitions of a forbidden nature from these states to the normal states of emission centres give rise to a temperature-independent, green-yellow phosphorescence, whose longest-lived component has a decay constant of 2 × 10 -5 sec -1 . Most yellow luminescent and non-luminescent diamonds (3,650 A. exciting radiation) exhibit a blue luminescence when excited by energetic particles or by X-rays, but no thermoluminescence is observed after any type of excitation. The luminescence of diamonds appears to be characteristic of the matrix crystal, and a tentative model for the emission centres is given.