Dynamics of local substructures in water observed by ultrafast infrared hole burning

Transient hole burning in the OH-stretching region of HDO dissolved in D₂O is investigated by two-color pump-probe spectroscopy in the temperature range 273–343 K. Spectral holes are observed with widths of 45 cm^-1 and a lifetime of ≈1 ps. The total OH band in the transient spectrum may be decomposed into three major constituents with different spectral and dynamical properties that are traced over the full temperature range. From the measured cross relaxation among the spectral components a structural relaxation time of 1.5 ± 0.5 ps (273 K) to 0.8 ± 0.4 ps (343 K) is inferred.