Laser Snow Effect in CS₂ Vapour

Abstract

The formation of micron-size particles in a gas system induced by laser radiation was reported for the first time by Tam, Moe and Happer [1] in 1975. In their experiment the argon laser beam passing through a gas mixture of caesium vapour, hydrogen and helium induced the formation of small white particles identified as caesium-hydride crystals. The observed phenomenon was called “laser snow.” Since then the laser snow effect has been observed in several gases illuminated by different laser lines [2–11]. Due to chemical reactions induced by laser light in a given gas system and subsequent condensation and coagulation processes small particles of size varying from 0.5 µ to 4 µ are formed. The particles cause intense scattering of laser light and they can be easily recognized by eye in the form of falling snow. A typical velocity of fall is of the order of mm/s.