The vibrational overtone spectrum of liquid methane in the visible and near infrared - Applications to planetary studies

The strengths of 10 bands in the absorption spectrum of liquid methane between 19,400 and 6190 A have been measured. After a small correction for the polarizability of the liquid is applied for the purpose of comparison with similar gas-phase measurements, it is found that there is no temperature dependence of the band strengths between 95 and 295 K. Changes of band shape with temperature cause the 95 K laboratory spectra to resemble Saturn more than room-temperature observations do. Gas-phase absorption clearly dominates the liquid in planetary spectra, so liquid methane cannot be detected in the outer solar system by earth-based observations.