H2O absorption thermometry accuracy in the 7321–7598 cm−1 range studied in a heated static cell at temperatures up to 1723 K

Abstract

Gas temperature may be inferred by comparing smoothed measurements of absorption spectra spanning >100 cm−1 to smoothed simulations of the same. Using this thermometry approach in a heated static cell at temperatures up to 1723 K, we studied H2O vapor absorption near 7450 cm−1, dominated by features in the R-branch of the v1 + v3 absorption band. In a first experiment, the cell was operated at 1200–1723 K and 0.0235 bar, while a commercial external cavity diode laser scanned the 7321–7598 cm−1 range. Temperatures inferred from the measured spectra using BT2 simulations were, on average, within 2 K of the actual cell temperature and fell within the limits of error (±0.5% of reading) for the thermocouple used to monitor gas cell temperature. Temperatures inferred using HITEMP2010 simulations were, on average, 38 K lower than actual cell temperatures. In a second experiment, the cell was operated at 296–1723 K and 1 bar while a swept-wavelength laser monitored the 7347–7536 cm−1 range at 10 kHz repetition rate. Temperatures inferred using BT2 simulations were within 3 K of the actual cell temperatures, within the limits of error for the gas cell thermocouple measurements.