High pressure sodium lamps have been subject to progressive reduction in pressure of contained sodium with attendant reduction in lighting quality. It has now been discovered that modification of lamp components permits the pressure of contained sodium to be maintained at higher levels. Emission materials enclosed within the lamp are altered to limit reactive oxygen in the lamp atmosphere. A thermionic electrode is equipped with an improved emission mix composition as illustrated in areas A and B of the triaxial plot of Figure 3 and an oxygen getter is intermixed with the mix composition. The oxygen getter is a metal which forms a highly stable oxide and may be at least one selected from the group consisting of titanium, zirconium, hafnium, tantalum and yttrium.