'The photochromic molecule, diarylethene, is considered to be a promising candidate for a molecular switch and memory. [M. Irie, Chem. Rev. 100 (2000) 1685.] Diarylethene derivatives have two thermally stable structures, i.e., open- and closed-ring isomers. The open-ring isomer is converted to the closed-ring isomer upon irradiation with UV light. Similarly, the open-ring isomer is obtained from the closed-ring isomer upon irradiation with visible light. Due to the distinctive difference in structure, especially the difference in the pi-conjugation, they have different absorption spectra.

Frequently, the IR spectrum of water is used to characterize the structure and strength of the associated hydrogen bond network. Our recent results show that linear IR spectroscopy alone is insufficient to predict effects on the structure and dynamics of water in different chemical environments based on qualitative assertions regarding the strength of the hydrogen bond network. Using nonlinear IR pump-probe spectroscopy we examine the dynamics of water in various chemical systems that have nearly identical IR absorption spectra.