Typically, the high-frequency excess is generally represented as a superposition of two to four damped harmonic oscillators. Fukasawa et al. report that the characteristic frequencies of the damped harmonic oscillators are 0.054, 0.079, 0.196, and 0.556 ps . Based on the isotopic shift analysis, the first two modes are suggested to represent librational modes of water molecules, while the third mode is interpreted as the vibration of oxygen atoms, reflecting hydrogen bond stretching. The final mode is attributed to the vibration of the entire water molecule, interpreted as hydrogen bond bending . Elton obtains O(10 -2 ) ps relaxations using the Brendel lineshape functions .