Optical Properties of Sodium in the Vacuum Ultraviolet*

Abstract

The index of refraction, n, of sodium films evaporated onto quartz substrates has been determined in the spectral region from 420 to 2000 Å from interference patterns observed in the reflected beam and from the critical angle marking the onset of “total reflection.” The growth of an oxide layer on the surface of a film is shown not to alter appreciably the position of interference maxima and minima. The real part of the dielectric constant was consistent with a nearly-free-electron model. The effective volume—plasmon energy was found to be 5.694±0.06 eV, in agreement with the values determined from electron-energy-loss experiments.