Rotational Temperature Meaasurements of N/2-Molecules Reflected from a Wall

Abstract

The interaction of N/2-molecules with high kinetic energy colliding with a solid hot wall is investigated by the electron beam fluorescence technique. It allows to measure the population of rotational levels of the molecules, which is necessary to define the rotational temperatures of the incoming (undisturbed) and the reflected molecules (coming back from the wall). Using pure N/2 or a NO/N/2 mixtures provides flow velocities up to 1500 m/s in a supersonic free jet expansion; seeding with light gas like He accelerates the flowing molecules up to 3100 m/s. The experimental results show a strong influence of the kinetic energy of the incoming flow, a minor influence of the wall temperature and the material, and an influence of the Knudsen number except for free molecular conditions.