Solubility of fluid helium in solid nitrogen at high pressure

Abstract

Experiments carried out at high pressures show that the transition of completely ordered solid \ensuremath{\epsilon}-${\mathrm{N}}_{2}$ to orientationally disordered \ensuremath{\delta}-${\mathrm{N}}_{2}$ is shifted over a factor of 2 in temperature or pressure due to the admixture of fluid helium. Between 5.4 and 11.0 mole % helium can be dissolved in \ensuremath{\epsilon}-${\mathrm{N}}_{2}$, favoring the occurrence of this ordered phase. In contrast, the transition from disordered \ensuremath{\delta}-${\mathrm{N}}_{2}$ to disordered \ensuremath{\beta}-${\mathrm{N}}_{2}$ is not shifted at all.