Measurement of the diffusion coefficient of sodium in neon at 530K

The diffusion coefficient D of sodium in neon has been measured at 530K. In a cylindrical discharge tube filled with neon at densities N of 10 23 to 10 24 m -3 a strong radial sodium density gradient is induced by means of a discharge current. In the afterglow of the discharge the decay rate of the fundamental diffusion mode is measured using dye laser absorption at the sodium D1 line. The value DN=(1.43+or-0.18)*10 21 m -1 s -1 is found. The diffusion coefficient is calculated for temperatures between 300 and 600K using Lennard-Jones (n-6) interaction potentials with n=12, 8 and 7, and using a Born-Mayer potential. Potential parameters are taken from the literature. Best agreement with experiment is found for the Born-Mayer potential and for the Lennard-Jones (7-6) potential.