The specific heat of solid oxygen

Measurements have been made in the temperature range from 1.3° K to about 71°K with particular attention to the behavior at very low temperatures, and in the neighborhood of the - transition at about 23.89° K. Assuming that near 0° K each molecule moves as a single mass point with the passage of lattice waves, the effective Debye temperature at 0° K is extrapolated to be 104±2° K. As the temperature rises above 10° K, the specific heat rises more rapidly than a reasonable Debye model would predict, suggesting the appearance of additional degrees of freedom, which are thought to be the superposition of a librational motion of the molecules superposed on the longitudinal and transverse lattice waves controlling the motion of a molecule's center of mass. The specific heat shows a very sharp high spike at the - transition with an entropy change of aboutR ln 1.65; there is no evidence for a latent heat associated with this transition.