Specific-Heat Anomaly in Solidified Gases due to O2 Impurity

A specific‐heat anomaly of Schottky type has been observed in the heat capacities of both solid CO and N₂, which is due to O₂ impurity. For both host lattices the peak of the anomaly is at $\text{T\hspace{0.17em}∼\hspace{0.17em}1.95°K}$ , and the shape corresponds to a two‐level system with a splitting of 5.14°K and a weight of 2 for the upper level. It is believed to be due to the spin splitting of the molecular oxygen ground state.