Effects of CO2 laser radiation on large orthophosphoric acid and water drops and on spherical ice crystals

An experimental investigation is reported of the conditions present during evaporation of suspended orthophosphoric acid and water drops, and of spherical ice crystals with a radius of the order of 1 mm when the laser radiation power density was 20–10⁴ W cm^-2 at the wavelength of 10.6 μm. The lower limit of explosive evaporation was determined for H₃PO₄ drops and ice crystals. Only one evaporation mechanism of H₃PO₄ drops was observed (this mechanism was explosive), but there were two mechanisms in the case of water drops (convective with vapour ejection and explosive) and spherical ice crystals (melting followed by evaporation of a water drop and explosive evaporation). Repeated explosions of H₂O drops were observed for a power density w = 10⁴ W cm^-2 when the beam diameter was 10 mm.