Radiative properties of a candle flame

Measurements are made of the spectral intensity of radiation from a candle flame in the optical region and the regions adjacent to it. The total luminous flux of the flame is determined. Measurements are made of spectral characteristics near the resonance transitions of sodium when a small amount of table salt is introduced into the flame. These characteristics are then analyzed. The optical radiation of the flame is produced by a region of the flame that is small compared to its visible part. The surface area of this region is $2.5 \pm 0.6$ cm$^2$. Its temperature is $1810 \pm 50$ K. Luminescence is created by fuel particles (clusters or aerosols). Here, a significant part or most of the fuel is in the particulate state (rather than the molecular state) in the radiative zone.