Explosive evaporation of Rb or K clusters by low-power laser radiation in the presence of excited atoms

Explosive evaporation of metallic Rb or K clusters in the presence of excited atoms stimulated by resonant CW laser radiation has been observed in a glass cell. Evaporation occurs at low laser-power density. The effect consists of the generation of optically thick and sharply localized alkali vapor clouds propagating in the cell against the laser beam. The clouds are charged and exhibit a strong luminescence of Rb or K spectral lines. The explosive evaporation of metallic clusters is explained by the laser excitation of alkali atoms, which collide onto the surface of the clusters and transfer their internal energy, which thereby causes other atoms to be evaporated and to continue the avalanche process.