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