Low temperature thermal conductivity measurements on solid neon at constant volume

The thermal conductivity of solid neon samples at constant volume was measured from 0.5 K to 10 K. An isotopically purified Ne-20 sample and a Ne-20 sample with 0.5% He-4 as well as a sample with the natural isotopic mixture was studied. These measurements were made at molar volumes between 13.4 cc/mole and 12.7 cc/mole. The enhancement of isotope scattering due to zero point effects was calculated to be between 25% and 150% using various theoretical estimates of the conductivity. Two conclusions were made independently of the theoretical approach, (1) the enhancement of scattering decreased with molar volume, and (2) the ratio of the enhancement for He-4 atoms in Ne-22 to that of atoms in Ne-20 is approximately 2. The high temperature thermal conductivity of the isotopically purified neon is observed to fall below that of natural neon of the same molar volume, in contradiction to the assumption that scattering processes are additive.