The electron hole pairs trapped within the active layer sensitize the activator ions, causing {HEAD ~ the activator ions} to emit {TAIL ~ light} 
to emit
The electron hole pairs trapped within the active layer sensitize the activator ions , causing { HEAD ~ the activator ions } to emit { TAIL ~ light }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL