Increase in the transparency of water vapor in vacuum ultraviolet under the action of giant laser pulses

An experimental investigation was made of the interaction of radiation pulses from a Q-switched neodymium glass laser with water vapor. Pulse-like increase in the transparency of the vapor was observed at the wavelength of probe radiation in the range 185–187 nm; this increase in the transparency increased on increase in the energy of the interacting pulses. The effect was clearly due to two-stage photodissociation of the water vapor molecules in the region of intersection of the interacting and probe radiations.