Photoinduced drift of sodium vapor in the absence of physical adsorption on the cell walls

An experimental study was made of a photoinduced drift of sodium vapor in helium in the absence of physical adsorption on the cell walls. The adsorption was prevented by treating the cell walls with the vapor of VM-1 diffusion pump oil. By eliminating physical adsorption, the time taken to establish a steady-state vapor density distribution was shortened by a factor of hundreds of thousands. The maximum drift velocity achieved experimentally was ~580 cm/sec. On the basis of these experiments, the relative change in the sodium diffusion coefficient as a result of optical excitation was estimated to be ~0.1.