A mechanism that gives rise to certain strong emission lines from ionized atoms of oxygen, carbon, and nitrogen in diffuse nebulae. Extremely hot stars and accretion disks (at temperatures of 30 000 K or more) produce copious amounts of extreme ultraviolet radiation at 30.4 nm from singly ionized helium atoms. These photons excite the ions of C III and N III in surrounding gas because the ions have a transition very close to this wavelength. These excited ions then return to the ground state by emitting a series of photons, including a group of lines in the 464–465 nm (blue) region. Bowen fluorescence also accounts for the exceptionally strong O III lines in the spectra of some planetary nebulae. The mechanism was identified by I. S. Bowen.