It's the second time that Mulder quotes Scully's thesis.
Howard Gordon and David Greenwalt wrote the screenplay in one intensive week of 15-hour days with contributions from John Shiban, Frank Spotnitz, and Ken Horton.
The molecule shown on the screen is a form of dichloroethane in which the four hydrogen atoms are replaced with helium. Although helium is highly unlikely to form a molecule in this way, the theoretical compound was simply intended to be something that didn't exist and that would be cold and unstable.