OPTICAL REFLECTIVITY AND ELECTRON MASS ENHANCEMENT IN EXPANDED LIQUIDCESIUM

Optical reflectivity data are reported for expanded liquid caesium ove r the range 144 degrees C (density, 1778 g cm(-3)) to 1100 degrees C ( density, 1.195 g cm(-3)) for photon energies 0.5 eV less than or equal to h omega less than or equal to 3.8 eV. Optical effective mass ratio s obtained from the plasma frequency are compared with mass ratios ext racted from analysis of the magnetic susceptibility. Both masses exhib it enhancements for liquid densities less than about 1.3 g cm(-3), sug gesting that expanded caesium gradually transforms to a highly correla ted metal below this density.