Every fluorescent light bulb on earth uses a small amount (several milligrams) of mercury. This element has seven naturally occurring isotopes. The opacity of the mercury vapor causes the resonance UV photons emitted by the atoms in a glow discharge plasma to be reabsorbed by adjacent atoms, leading to a much longer effective lifetime or lower escape rate of photons before they can reach the phosphor coating on the inner wall of the lamp envelope. Aong the way, collisions quench radiating states, which amounts to a loss of efficiency. It was long recognized that adding more of the rare Hg-196 isotope to natural mercury enhances the radiation escape rate and yields higher efficiency, with a modest improvement of up to 7%.
Researchers at The University of Texas at Austin have developed a new isotopic composition of the mercury that will yield drop-in replacement lamps with enhanced performance compared to existing fluorescent lamps. The new composition parameter increases the enhancement of 16% in the escape rate of resonance UV radiation. The exact composition of mercury may be found in the associated issued patents.