We report the background-free observation of atomic antihydrogen, prod
uced by interactions of an antiproton beam with a hydrogen gas jet tar
get in the Fermilab Antiproton Accumulator. We measure the cross secti
on of the reaction <(p)over bar p> --> <(H) over bar e(-) p for (p) ov
er bar beam momenta between 5203 and 6232 MeV/c to be 1.12 +/- 0.14 +/
- 0.09 pb.