Infra-Red Spectroscopic Study of Structural Change of Liquid Water Induced by Sunlight Irradiation

Summary Distinct changes in the infra-red (IR) spectrum of liquid water in the O-H stretching region were observed on irradiation of sunlight at room temperature. The spectrum shape in the range 2 800 – 3 800 cm -1 became trapezoidal on irradiation of the sunlight for more than 30 minutest under the sunlight strength of 3 MJ m -2 . The spectrum gradually changed to restore the original spectrum in 180 minutes when sunlight irradiation was shut off. These results indicate that the formation and elimination of a clathrate-like structure of water occur reversibly at room temperature in response to irradiation and shutoff of the sunlight, respectively. The structural change caused by the sunlight irradiation occurs over a period of several minutes to hours.