Abstract:
A high pressure mercury vapor (HPMV) discharge lamp of the additive type having a discharge sustaining filling which includes mercury from about 2.0 to 4.0 milligrams per cubic centimeter of arc tube volume, thallium iodide and sodium iodide in a combined amount of from about 1.0 to 2.5 milligrams per cubic centimeter of arc volume, zirconium iodide in an amount of about .03 to 0.3 milligrams per cubic centimeter of arc tube volume and a small quantity of inert ionizable starting gas whereby upon operation of the lamp a spectral distribution is produced which includes in addition to the sodium and thallium peaks a substantial continuum from the blue to the red.