title: Experimental evidence of Fermi resonances in isotopically dilute water from ultrafast broadband IR spectroscopy.
abstract: The vibrational dynamics of liquid water, which result from a complex interplay between internal molecular vibrations and the fluctuating hydrogen bond network, are fundamental to many physicochemical and biological processes. Using a new ultrafast broadband mid-infrared light source with over 2000 cm(-1) of bandwidth, we performed ultrafast time-resolved infrared spectroscopy to study the vibrational couplings and relaxation dynamics of the stretching and bending vibrations of the mixed isotopologue, HOD, in D2O. Analysis of cross-peaks and induced absorptions in the two-dimensional infrared spectrum and transient absorption spectrum shows that the hydroxyl stretch of HOD is coupled to the HOD bending mode via Fermi resonance, with a 70° angle between their transition dipole moments. We see that HOD is also anharmonically coupled to the D2O solvent modes. From transient absorption spectra, we conclude that vibrational relaxation occurs through a number of paths. The strongly hydrogen-bonded OH oscillators have the highest propensity to relax through the bending mode, while the weakly hydrogen bonded oscillators relax through other modes.
authors: Department of Chemistry, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors: Luigi
authors: L
authors: De Marco
authors: Krupa
authors: K
authors: Ramasesha
authors: Andrei
authors: A
authors: Tokmakoff
mesh_terms: D017666:Deuterium Oxide / Q000737:chemistry; D006860:Hydrogen Bonding; D013055:Spectrophotometry, Infrared; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D017666:Deuterium Oxide