Laser-Cooling of Liquid Water by the Ar-Xe Laser Radiation

TL;DR

This study reports the first observation of laser-induced cooling in liquid water using Ar-Xe laser radiation, resulting in a temperature decrease and formation of quasi-stable molecular clusters with long lifetimes.

Contribution

It demonstrates for the first time laser cooling of water via vibrational excitation and cluster formation, revealing long-lived excited states induced by laser irradiation.

Findings

Water temperature decreased by 2.2 K after laser irradiation.

Excited vibrational states of H2O have lifetimes of hours.

The excited states can persist for hundreds of seconds due to radiation trapping.

Abstract

An effect of laser-cooling of water was observed for the first time with a temperature decrease dT = -2.2 K after irradiation of liquid water surface by a powerful Ar-Xe pulse laser with a pulse energy of about 1 J and wavelength L = 1.73, 2.63 and 2.65 um. The discovered effect can apparently be ascribed to the optical excitation of vibrational states of H2O molecules followed by an endothermic consolidation of chemically active excited molecules into a quasi-stable cluster-like structure. The measured time dependences of the cooling effect show that a typical life time of the new state of water amounts to hours. It has also been shown that the life time of the excited vibrational molecular states due to a radiation trapping effect can be estimated to at least hundreds of seconds.