Density of , and ices at different temperatures of deposition

In this work the density ( ρ ) and the real part of the refractive index ( n ) of frozen methane, nitrogen and carbon dioxide were obtained in the laboratory. The densities are given for different temperatures of deposition between 10 K and the sublimation temperature of these molecules in our experimental setup ( p ⩽ 10 - 7 mbar ) . We have found that methane and nitrogen have a constant value in all the interval of the studied temperatures for both ρ and n . Carbon dioxide, on the contrary, has important variations for both physical parameters (up to 50% in density) revealing important structural changes.