Normal spectral emissivity of undercooled liquid silicon

Normal spectral emissivities of silicon in the stable and undercooled liquid state (1553-1797 K) have been successfully measured over a wavelength range between 550 and 1600 nm with an electromagnetic levitator. The spectral emissivities of liquid silicon have negligible temperature dependence. Therefore, it is justified that the value of the emissivity calibrated at the melting point can be applied in a wide temperature range for pyrometric temperature measurements. The spectral emissivities exhibit weak negative wavelength dependence and these are in good agreement with the values estimated by the Drude free-electron model.