A FEASIBILITY STUDY OF THE MEASUREMENT OF ION DENSITIES BEHIND AIR SHOCKS BY INTRODUCING SMALL AMOUNTS OF LITHIUM VAPOR

Abstract : Preliminary experiments indicated that ionization equilibrium is attained in the shock tube behind strong shocks in argon and that the boundary layer appears to electrically insulate the gas from the metal tube walls. The anomalous method was used to measure the amounts of lithium vapor injected into the shock heated air and it is concluded that concentrations of 300 ppm could be maintained within a factor or two. Experimental data is presented which suggest that the presence of the lithium vapor has no great effect upon either the vibrational relaxation rate of nitrogen or the overall dissociation rate of oxygen. Interferometric evidence indicated that the bulk dissociation processes did equilibrate behind M 18 shock waves in air although Stark measurements by the 4603 Angstrom lithium line suggest that ionic equilibrium is not attained. (Author)