Dielectric anomalies of solid CO and N_2 in the audio frequency range

We report the first audio frequency dielectric constant measurements of CO and N_2 in their solid phases. We have observed several new features, including (1) strong hysteresis effects above an onset temperature $T_{h} \simeq 42 K$ in the \beta-phase of pure N_2, (2) absence of the expected short range antiferroelectric dipolar ordering in CO down to 4.2 K, and (3) anomalous temperature dependence of the dielectric constant in the \alpha-phases of both CO and N_2. Quantum mechanical treatment of the molecular rotation explains some of the observed anomalies in the \alpha-phase, but the strong hysteresis indicates that pure geometrical frustration plays a significant role in the \beta-phase.