A study on REMPI as a measurement technique for highly rarefied gas flows (Simulations and its fundamental properties of REMPI spectra)

Nowadays, a non-intrusive measurement tool of thermodynamic variables with high sensitivity is strongly demanded for analyses of highly rarefied gas flows. REMPI (resonantly enhanced multiphoton ionization) is the most suitable technique for measurement of gas molecules with very low density. In this study, to examine the fundamental properties of the REMPI spectra, 2R+2 N₂-REMPI spectra including the spectral broadening are calculated and compared with the experimental results. From the calculated REMPI spectra, spectral lines adequate to measure temperature are proposed, especially at relatively high temperature where the measurement error becomes larger because of the overlap of the spectral lines.