Method and system for instantaneously determining the temperature of a low density gas using ensemble ratioing of laser-induced fluorescence peaks

摘要

A method and system are provided for determining temperature of a low density gas seeded with molecules of iodine. The Cordes bands of the iodine molecules are excited with light energy of a known wavelength (e.g., between 175-210 nanometers) to generate fluorescent emission. At least a portion of the emission's light intensity is collected and used to generate an emission spectrograph. The spectrograph's vibrational energy level peaks are fitted to a vibrational Boltzmann distribution. Specifically, one of the vibrational energy level peaks associated with molecule population in a ground vibrational energy level at a wavelength greater than the known wavelength of the light energy is selected. Next, a plurality of ratios are generated that define a unique linear relationship for a temperature of the seeded environment. Each of these ratios is defined by a ratio of the selected one of the vibrational energy level peaks (in a ground vibrational energy level) to another unique peak (of the vibrational energy level peaks) associated with molecule population in a vibrational energy level that is greater than the ground vibrational energy level.