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