Light emission during adsorption and desorption of oxygen on magnesium oxide

Chemisorption of oxygen on a previously outgassed MgO sample is accompanied by a luminescence phenomenon which follows an Elovitch kinetic law. Heating the MgO sample in vacuo after O₂ adsorption causes the appearance of strongly correlated thermally stimulated desorption (TSD) and luminescence (TSL) peaks. Analysis by the least-squares method shows that thermostimulated spectra prove to be the superposition of one second-order peak and one (TSL) or two (TSD) first-order peaks. The observed compensation law and the strong correlation between activation energy and preexponential factor are discussed. On the basis of our experiments a tentative mechanism about light emission is also proposed.