Infra-Red Spectroscopic Study of Structural Change of Liquid Water Induced by Sunlight Irradiation
Yokono T1, Shimokawa S*2, Yokono M3, Hattori H4
1Techno-Science Laboratory, CRIS, Hokkaido University, Kita-ku, Kita-21, Nishi-10, Sapporo 001-0021, Japan; E-mail: tyokono@me.com
*2 Techno-Science Laboratory, CRIS, Hokkaido University , Kita-ku, Kita-21, Nishi-10, Sapporo 001-0021, Japan; E-mail: shimokawa@cast.hokudai.ac.jp
3Institute of Low Temperature Science , Hokkaido University, Kita-ku, Kita-19, Nishi-8, Sapporo 060-0819, Japan; E-mail: filia@mac.com
4Catalysis Research Center, Hokkaido University , Kita-ku, Kita-21, Nishi-10, Sapporo 001-0021, Japan; E-mail: hattori@cat.hokudai.ac.jp
Correspondence: shimokawa@cast.hokudai.ac.jp
Key Words: Liquid water; Sunlight irradiation; Clathrate-like structure; IR of O-H stretching.
Received 15 October 2008; revised 9 January 2009; accepted 11 March 2009. Published 1 July 2009. Available online: 1 July 2009.
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 2800 – 3800 cm -1 became trapezoidal on irradiation of the sunlight for more than 30 minutes 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.