Abstract

An electrodeless lamp includes a light transmissive envelope and a fill disposed in the envelope where the fill has the characteristic of emitting light when ignited and is excited by high frequency electrical energy provided by an R.F. or microwave source. The lamp includes a fill material enabling more reliable and effective ignition and shorter restrike intervals after an operating lamp has been extinguished. The fill includes a first component (preferably sulfur, selenium or a mixture of sulfur and selenium) and a second component (preferably xenon gas) included at a partial pressure in the range of 50 to 200 torr. A third component (preferably argon gas) is included at a partial pressure in the range of 5 to 20 torr. Preferably, approximately 5 torr of argon is added to a selected fill pressure of xenon (e.g., a partial pressure of 100 torr or more). The addition of a low partial pressure of argon provides unexpected improvements in starting and reduction in restrike time while maintaining a high lamp efficacy.