An improved method for the estimation of rotational temperature with a weak electron beam

Abstract

In this paper, an improved method for the estimation of rotational temperature with a weak electron beam is presented. Using the method, the effect of an electron beam on a flow field becomes smaller and it is possible to obtain the distribution of rotational temperature with a smaller experimental apparatus. In the method, slit width of a monochromator is set wider to obtain larger signals for the higher rotational levels. Due to the decrease of resolution, the rotational spectra are measured with much overlapping, but they are divided into their individual rotational spectra by using a fitting function, Using the improved method, a rotational temperature and a relative number density distribution in a supersonic nitrogen free jet expanding from a stagnation temperature of 350 K is measured. Moreover, the experimental results are compared with theoretical results based on master equations and those simulated by the Direct Simulation Monte Carlo (DSMC) method using the Dynamic Molecular Collision (DMC) model. These results are consistent with each other, enabling verification of the experimental results.