The magnetic susceptibility of oxygen in a clathrate compound

The magnetic susceptibility of oxygen enclosed in a β-quinol clathrate compound has been measured at temperatures from 1 to 20° K. Its behaviour is compared with that calculated for a gas of non-interacting oxygen molecules over the same range of temperature. At high temperatures such a gas would obey Curie’s law, but owing to the restriction to odd values of rotational quantum number, the susceptibility of a gas of 16O 16O molecules would depart from Curie’s law at temperatures below 10° K. It is found that at temperatures above 2°K the susceptibility of the oxygen in the clathrate compound agrees within the experimental error with the calculated susceptibility. Below 2°K, however, they do not agree, nor is any difference observed between oxygen of normal isotopic constitution and oxygen enriched to 11 % in 16O 18O, whereas the magnetic susceptibility calculated for an enriched specimen of the free gas would differ appreciably from that of the normal gas at temperatures below 2°K.