ANOMALOUS TEMPERATURE-DEPENDENCE OF THE DESORPTION OF EXCITED SODIUM ATOMS INDUCED BY ION-BOMBARDMENT OF SODIUM-FLUORIDE CRYSTALS

We have observed anomalous temperature dependence in the ion-induced d esorption of excited sodium atoms from sodium fluoride crystals. The f luorescence yield of the 3p-3d transition at 8195 Angstrom, and the 3p -4d transition at 5688 Angstrom increases steadily with temperature; h owever the yield of sodium doublet 3s-3p transition displays a pronoun ced maximum in the region of 160 degrees C. Fluorescence yields are al so found to be nonlinear as a function of beam current at room tempera ture. To explain these experimental results, we propose a mechanism th at involves electron transfer between the desorbing atoms and the bomb arded surface.