As the father of nuclear physics, Ernest Rutherford is credited with splitting the atom in 1917. His team in England bombarded nitrogen with naturally occurring alpha particles from radioactive material and observed a proton emitted with energy higher than the alpha particle. In 1932 two of his students John Cockcroft and Ernest Walton, working under Rutherford's direction, attempted to split the atomic nucleus by entirely artificial means, using a particle accelerator to bombard lithium with protons, thereby producing two helium nuclei.