Finally, in Fig. , we analyze the effective modes responsible for the appearance of the absorption bands at around 1350 cm -1 (left panels) and 1850 cm -1 (right panels). The effective modes at lower frequency appear to be slightly different, as in water no umbrella motion involving the CH 3 fragment could be discerned, but rather a combination of HCH bending and CH vibration. As ω5=1313 cm -1 (h.) ω13=1835 cm -1 (h.)