Field took a position as an instructor at the
University of Texas at Austin in 1947 and became an assistant professor in 1949. In 1952, he took a position as a research chemist at
Humble Oil in
Baytown, Texas, where he, along with
Burnaby Munson, discovered chemical ionization. In 1966, he moved to
Esso Research and Development Company in
Linden, New Jersey, where he rose through the ranks to become a senior research associate. In 1970 he took a position as a professor at
Rockefeller University and became emeritus in 1989. ==Awards and honors==