whereby laser stimulated phtoelectron emissions are differentiated over {HEAD ~ a threshold} for {TAIL ~ detection} 
for
whereby laser stimulated phtoelectron emissions are differentiated over { HEAD ~ a threshold } for { TAIL ~ detection }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL