Temperature dependence of vibrational relaxation of the OH bending excitation in liquid H2O

► The energy relaxation of the OH bending vibration in pure liquid H2O was found to show anomalous temperature dependence. ► The population lifetime increases from 170 fs at T = 295 K to 250 fs at T = 348 K. ► The observed temperature dependence supports the relaxation scenario that the bend vibrational energy is dominantly transferred to librational motions.