We have studied the equilibration dynamics of liquid water and alcohols following a local deposition of energy using time-resolved femtosecond mid-infrared pump-probe spectroscopy.The equilibration dynamics is monitored via the spectral response of the OH-stretch vibration.It is found that the equilibration leads to complicated changes of the absorption band of the OH-stretch vibration including a shift of the absorption band and a decrease of the absorptin cross section.Interestingly,these spectral changes do not occur simultaneously,which indicates that they are associated with the equilibration dynamics of different low-frequency modes.For water,we find an equilibration time constant of 0.55(+-)0.05 ps.We observe that the equlibration time strongly increases going from water to alcohols such as methanol,ethanol,and propanol which means that water molecules can adapt much faster to a local deposition of energy than other hydrogenbonding liquids.
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