Аннотация:A series of probe measurements to determine the electron concentration in the gas ahead of astrong shock wave (SW) front are carried out using a modified double-diaphragm shock tube (DDST-M) ofthe Institute of Mechanics, Moscow State University. At the same time, the light flux from the region of theshock-heated gas is recorded, which makes it possible to calculate the electron concentration behind the SWusing the spectroscopic method. The experiments are carried out in air, oxygen, and nitrogen at SW velocitiesranging from 8.3 to 11.3 km/s and an initial pressure of 0.25 Torr in the low-pressure chamber (LPC). Thedependencies of the electron concentration on the SW velocity and the distance from the observation pointto the SW are obtained. The spectroscopic measurements make it possible to determine the dependence ofthe electron concentration on the composition of the gaseous medium. The obtained data are compared withthe experimental data of other authors.