MIXING OF LONGITUDINAL AND TRANSVERSE DYNAMICS IN LIQUID WATER

Molecular dynamics simulations of liquid water in the 1.3-35 nm(-1) mo mentum transfer (Q) region show two excitations with a Q dependent sym metry character. The symmetry analysis suggests that the observed anom alies in the high frequency collective dynamics originate from relaxat ion processes responsible for (i) the appearance of a propagating tran sverse dynamics at high frequency, (ii) the transition from normal to fast sound, and (iii) a mixed symmetry of the two modes at large Q.