Page "Flashtube" Paragraph 21

Higher current densities begin to produce continuum emission.

Spectral lines are less dominant as light is produced across the spectrum, usually peaking, or " centered ", on a certain wavelength.

Optimum output efficiency in the visual range is obtained at a density that favors " greybody radiation " ( an arc that produces mostly continuum emission, but is still mostly transparent to its own light ).

For xenon, greybody radiation is centered near green, and produces the right combination for white light.

Greybody radiation is produced at densities above 2400 A / cm < sup > 2 </ sup >.