  The optical properties of LXe in the vacuum ultra violet (VUV), determining
the performance of a scintillation calorimeter, are discussed in detail. The
available data, measured in a wider spectral region from visible to UV light,
and in a large range of Xe densities, from gas to liquid, are examined. It is
shown that this information can be used for deriving the LXe optical properties
in the VUV. A comparison is made with the few direct measurements in LXe for
VUV light resulting from the LXe excitation by ionizing particles. A useful
relation is obtained which connects the Rayleigh scattering length to the
refractive index in LXe.
