Effects of initial humidity and temperature on laser-filamentation-induced condensation and snow formation.

We investigated the effects of initial humidity and temperature on the formation of water condensation and various snowflake patterns by firing high-repetition filaments of femtosecond Ti-sapphire laser pulses at 9 mJ/50 fs per pulse into a cloud chamber. While adjusting initial temperature and humidity distributions near the filaments, snowflakes and ice particles with various shapes and sizes were observed on the bottom cold plate. In addition, significant differences were found in the weights of the laser-induced snow below the filament center. From those data, initial conditions of low temperature (<−15 °C) and high humidity (relative to water RH > (90 ± 11) % and to ice RH > (120 ± 15) %) were found being important to assist an efficient laser-filamentation-induced condensation and snow formation. [ABSTRACT FROM AUTHOR]