The method 1 including collecting gas molecules containing the other of {TAIL ~ said isotopes} traveling along said {HEAD ~ other path} 
The method 1 including collecting gas molecules containing the other of { TAIL ~ said isotopes } traveling along said { HEAD ~ other path }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD