New experimental measurements and theoretical analysis of the collision-induced absorption in N2-H2 pairs

We present new experimental data on the collision-induced fundamental absorption in N2-H2 mixtures at room temperature and at low enough pressures so that the binary contribution is dominant. Previous measurements have been made at pressures where the ternary and possibly higher absorption coefficients are significant, and this makes it difficult to obtain accurate values for the binary absorption enhancement coefficient. To obtain the enhancement spectrum from the measurements of the mixture, it is necessary to subtract out both the spectra of pure H2 and N2, along with some CO2 impurities thus increasing the experimental uncertainty. Nevertheless, we obtain a value for the integrated intensity of 1.15×10−4 cm−2 amagat−2 that is in good agreement with the previous value of 1.38×10−4. We also discuss how one can scale this result to high temperatures for application to brown dwarf or methane dwarf atmospheres.