candoluminescence

The light is produced by a combination of incandescence and candoluminescence.

In this scenario, observations of candoluminescence would simply have been underestimating the temperature of the emitting species.

Early in the 20th century, there was vigorous debate over whether candoluminescence is required to explain the behavior of Welsbach gas mantles or limelight.

The higher temperature would then lead to higher emission levels in the visible portion of the spectrum, without invoking candoluminescence as an explanation.

One important candoluminescence mechanism is that the candoluminescent material catalyzes the recombination, enhancing the intensity of the emission.

There is also some evidence that the emission is enhanced by candoluminescence, the emission of light from the combustion products before they reach thermal equilibrium.

Candoluminescence is the light given off by certain materials at elevated temperatures (usually when exposed to a flame) that has an intensity at some wavelengths which can be higher than the blackbody emission expected from incandescence at the same temperature.

The modern scientific consensus is that candoluminescence does occur, that it is not always simply due to selective thermal emission, but the mechanisms vary depending on the materials involved and the method of heating, particularly the type of flame and the position of the material relative to the flame.

In any case, the key feature of candoluminescence is that the combustion products lose their energy to radiation without becoming thermalized with the environment, which allows the effective temperature of their radiation to be much higher than that of thermal emission from materials in thermal equilibrium with the environment.

Several authors in the 1950s came to the view that candoluminescence was simply an instance of selective thermal emission, and one of the most prominent researchers in the field, V.A. Sokolov, once advocated eliminating the term from the literature in his noted 1952 review article, only to revise his view several years later.

Some more recent authors seem to have concluded that neither Welsbach mantles nor limelight involve candoluminescence (e.g. Mason), but Ivey, in an extensive review of 254 sources, concluded that catalysis of free radical recombination does enhance the emission of Welsbach mantles, such that they are candoluminescent.