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