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An intense laser-induced fluorescence of sodium and of other alkali atoms (K, Rb) at room and lower temperatures has been observed in polysiloxanecoated cells, producing a vapor density of the metal which is much higher than that corresponding to the thermal equilibrium between the vapor and the condensed phase. This enhancement is attributed to the light-induced ejection of atoms absorbed by the polysiloxane coating. The atomic density of the vapor can be manipulated by changing either the laser power or frequency. The dependence of the atomic density on these and other parameters as well as its time-dependent behavior are studied experimentally. A tentative interpretation of the phenomenon is discussed in terms of the properties of solutions of the alkali metals in several solvents.PACS 32.80 -Photon interactions with atoms. PACS 32.80.Fb -Photoionization and photodetachment.

The excitation of triboluminescence by elastic and plastic deformation and by fracture of single crystals has been studied in detail by means of a high sensitive experimental apparatus. Typical results are reported for crystals of ZnS(Mn), NaCl(Mn), X‐ray‐irradiated KI and KCl, and sugar. The experiments show that the characteristic light peaks of triboluminescence are intimately related to the treads occurring in the stress–strain curves. A detailed analysis of these curves in different materials suggests two excitation mechanisms for triboluminescence: 1. excitation by impact of moving dislocations with trapped electrons; 2. excitation by unpinning of dislocations from luminescent centres.