The number of metallic probes can be controlled to thereby control {HEAD ~ the amount} of {TAIL ~ metallic ions} produced 
The number of metallic probes can be controlled to thereby control { HEAD ~ the amount } of { TAIL ~ metallic ions } produced
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH