Optical properties of copper and gold in the vacuum ultra-violet

The optical constants of copper and gold have been determined over a range of wavelengths from 4600 Å to 460 Å by measuring the reflection coefficient for unpolarized light at four angles of incidence. The results are expressed by means of graphs of 1 and 2, the real and imaginary parts of a complex dielectric constant, against photon energy, from 1 to 26 eV. They agree with recent determinations by Roberts and by Otto in the visible, but disagree somewhat with the work of Ehrenreich and Philipp and of Canfield, Hass and Hunter in the ultra-violet. Precautions were taken to avoid surface distortion and contamination and to correct for stray light, and it is claimed that on this account the present data, where they depart from the old, are to be preferred. The Kronig-Kramers relations are used to show that the data are internally consistent and also to suggest how they may be extrapolated to higher and lower energies.