Transient absorption of vibrationally excited water

We study the spectral response of the transition between the first and the second excited state of the O–H stretch vibration of HDO dissolved in liquid D₂O with two-color femtosecond mid-infrared spectroscopy. The spectral response of this transition differs strongly from the fundamental absorption spectrum of the O–H stretch vibration. In addition, excitation of the O–H stretch vibration is observed to lead to a change of the hydrogen-bond dynamics of liquid water. We show that both these observations can be described with a refined quantum-mechanical version of the Lippincott–Schroeder model for hydrogen-bonded OH.O systems.