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