Stable, continuous-wave light sources at 172 nm, based on the Xe2* excimer molecule, with conversion efficiency of electrical energy to vacuum ultraviolet (VUV) light greater than 50%, are reported. In high-pressure xenon gas, “Saint Elmo’s Fire” corona discharges serve as localized point electron sources with a metal grid at a few kilovolts providing an accelerating electric field. An extended VUV light-emitting region with high-energy conversion efficiency indicates that electron energy loss is predominantly by excitation of Xe atoms rather than by ionization. A room-temperature prototype lamp with variable VUV power to 35 mW/cm2 has been demonstrated. © 2003 American Institute of Physics.