Mass spectrometry was used to monitor the permeation of He through monocrystalline membranes of the halide. The diffusion data could be described by:

D (cm2/s) = 1.4 x 10-2 exp[-0.34(eV)/kT]

R.C.Wayne: Physical Review B, 1973, 8[6], 2958-64

The best linear fits to the solute diffusion data ([336] to [347]) yield:

Ar: Ln[Do] = 0.77E – 13 (R2 = 0.98); Br: Ln[Do] = 0.49E – 18.3 (R2 = 0.88);

He: Ln[Do] = 1.17E – 15.9 (R2 = 0.58)