{HEAD ~ A solid material} or combination of {TAIL ~ materials} is evaporated in the chamber to form vapor 
of
{ HEAD ~ A solid material } or combination of { TAIL ~ materials } is evaporated in the chamber to form vapor
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH