The discharge vessel encloses a discharge space having an ionizable filling which, in addition to Hg, contains a quantity of iodide of Na, {TAIL ~ Tl}, Ho and {HEAD ~ Ca} 
The discharge vessel encloses a discharge space having an ionizable filling which , in addition to Hg , contains a quantity of iodide of Na , { TAIL ~ Tl } , Ho and { HEAD ~ Ca }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD