THERMAL EFFECTS ON THE DYNAMICS AND ELECTRONIC STATES OF NA3C60

Raman-scattering and ultraviolet-photoemission measurements on Na3C60 thin films indicate a transition at elevated temperatures to a system with increased metallic character. This is observed by a substantial i ncrease in line widths and peak shifts of selected Raman H(g)(i) modes accompanied by an increase in the density of states at the Fermi ener gy as measured by photoemission. Changes in these spectra with tempera ture, as well as differences with K3C60 and Rb3C60, suggest that low-t emperature nonmetallic behavior is due to octahedral Na site disorder.