fluorescence

Concise Oxford English Dictionary © 2008 Oxford University Press:
fluorescence /flʊəˈrɛs(ə)ns, flɔː-/

▶noun light or other radiation emitted by a substance when it is exposed to incident radiation of a shorter wavelength such as X-rays or ultraviolet light.

■ the property of emitting light in this way.

– origin C19: from fluorspar (which fluoresces), on the pattern of opalescence.