Strong feedback effect in the vibrational relaxation of liquid water

We show the presence of a strong negative feedback effect in the vibrational relaxation of the O–H stretch vibrations of liquid H2O. The vibrational relaxation of an O–H stretch vibration leads to the excitation of strongly coupled low-frequency modes, which induces a deceleration of the relaxation of other still excited vibrations. We present a model for this feedback effect, with which we obtain a consistent interpretation of the experimental results of recently reported femtosecond mid-infrared pump–probe experiments and mid-infrared pump anti-Stokes Raman probe experiments.