This microscopic measure of light intensity equals ten to the negative fifteenth power candelas. Optical physicists use it to quantify the emission of single photons or extremely faint luminescence from quantum dots and single molecules. It represents a level of brightness far below the detection threshold of the human eye, requiring highly sensitive photomultiplier tubes to measure.
Heard on the job
The quantum dot emission peaked at roughly fifty femtocandelas under standard excitation.