Slow dynamics due to the metal–non-metal transition in liquid mercury

Abstract The sound absorption coefficient, α , of expanded liquid mercury has been measured at 20, 32 and 44 MHz in the temperature and pressure range up to 1600 °C and 210 MPa. Besides the critical attenuation, we have observed an anomalous increase of α due to the relaxation process in the metal–non-metal (M–NM) transition range. Assuming a Debye-type relaxation, we show that the relaxation time, τ , is about 2 ns and the relaxation strength has a broad maximum in the M–NM transition range. Introducing a simple model in which the ionization equilibrium is considered, we conclude that the anomalous dynamics should be closely related to the promotion of the 6s electron to the 6p states.