Ions with a specific mass to charge {HEAD ~ ratio} may selectively pass through the duct and impinge on {TAIL ~ the substrate surface} 
Ions with a specific mass to charge { HEAD ~ ratio } may selectively pass through the duct and impinge on { TAIL ~ the substrate surface }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL