CS-133 HIGH-PRESSURE MOSSBAUER-SPECTROSCOPY - A NEW POWERFUL TOOL FORSTUDYING CHARGE-TRANSFER AND LATTICE-DYNAMICS IN METALLIC CS

The purpose of this paper is to illustrate that Cs-133 high pressure M ossbauer effect (ME) spectroscopy is an ideal technique to investigate on a microscopic level the pressure effects on charge transfer and la ttice dynamics in metallic Cs. After discussing the experimental diffi culties, which have been the reason for the lack of Cs-133 ME studies on metallic Cs since 1965, we show that the results reveal first direc t microscopic evidence for a pressure induced 6s --> 5d electronic tra nsition in metallic Cs. We further investigate the change of Debye tem perature with pressure at 4.2 K and obtain a new value of the Debye te mperature of metallic Cs of Theta(D) = 64(2) K at p = 6 GPa. Special e mphasis is given to the comparison of the experimental results with re cent band structure calculations.