Knowledge Bank

Measurements of the spectral emissivities have been made for $H2O$ between 1 and $10\mu$ in the temperature range from $500\circ$ to $2300\circ K$. This spectral region includes the two strong fundamental bands at 6.3 and $2.7\mu$, and the three weak combination bands at 1.87, 1.34 and $1.1\mu$. The hot $H2O$ samples were produced in a small supersonic burner using $H2$ and $O2$. The spectral measurements were made at the exit of the burner where the temperature, concentration and total pressure could be defined. The spectral emissivities of $H2O$ were determined from calibrated infrared emission spectra and accurate spectroscopic determinations of the gas temperature. The emissivity spectra were used to obtain the absolute integrated intensities of the various bands of $H2O$ at the elevated temperatures. The experimental results show that the integrated intensities of the two fundamental bands of $H2O$ are independent of temperature, while the integrated intensities of the three combination