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

The sound absorption coefficient, a, of expanded liquid mercury has been measured at 20, 32 and 44 MHz in the temperature and pressure range up to 1600 degreesC and 210 MPa. Besides the critical attenuation, we have observed an anomalous increase of alpha 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, T, 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. (C) 2002 Elsevier Science B.V. All rights reserved.