Compositions of mercury isotopes for lighting

Described herein is a mercury sample that has an isotopic composition that differs from the naturally occurring distribution of isotopes. In various configurations of an isotopically tailored mercury sample, the fraction of one or more isotopes is increased or decreased with respect to the natural fraction(s). A example of a lighting device comprises an envelope, a buffer gas enclosed within the envelope, a isotopically tailored sample of mercury vapor, and a current injection mechanism configured to excite the mercury vapor to emit light. In various configurations, the lighting device emits radiation at a wavelength of 254 nm and/or at a wavelength of 185 nm. In various configurations, the lighting device envelope includes a fluorescent coating that is excited by ultraviolet (UV) light emitted by the mercury vapor. In various configurations, the lighting device provides improved efficiency as compared to lamps employing mercury with a naturally occurring isotope distribution.