Density and refractive index of binary CH4, N2 and CO2 ice mixtures

In this work we present the results of a series of laboratory experiments performed to obtain the density and the real part of the refractive index of binary mixtures of ices of astrophysical interest. Densities of CO2:CH4 mixtures obey the expected weighted mean and the other binary mixtures have densities up to 20% lower than expected. Refractive index for all the binary mixtures deviates up to 5% from the theoretical, obtaining higher values than expected for CO2:CH4 and lower values than predicted for CO2:N2 and CH4:N2.