hg08
commented
2 years ago Although conventional SFG spectroscopy can provide structural information about an interface, in the case of water, where the spectrum is dominated by inhomogeneous broadening, it is unable to probe the dynamics. To study dynamics, one-dimensional (1D)SFG needs to be extended to two dimensions (2D), much like IR spectroscopy has recently been extended to 2DIR. [NiYicun2012,PNAS] In a time-domain 2DIR experiment, the sample is subjected to three IR pulses, separated by two time intervals t1 and t2, and the signal is heterodyne detected at a time t3 later. The signal is then Fourier transformed in t1 and t3, leading to two frequency dimensions ω1 and ω3. A series of 2DIR spectra is collected as a function of t2, the “waiting time.” Roughly speaking, the 2DIR spectrum can be thought of as the joint probability density that the chromophore has frequency ω1 at time 0 and ω3 at time t2. Thus, the experiment naturally reports on dynamic processes such as spectral diffusion and chemical exchange (53). 2DIR spectroscopy has been widely used to study dynamics in bulk water, including hydrogen-bond dynamics (54–60),
2D-SFG has been used in Hydrogen bond dynamics? What have been obtained?