With Melba Phillips, the first graduate student to begin her PhD under Oppenheimer's supervision, Oppenheimer worked on calculations of artificial radioactivity under bombardment by deuterons. When Ernest Lawrence and Edwin McMillan bombarded nuclei with deuterons they found the results agreed closely with the predictions of George Gamow, but when higher energies and heavier nuclei were involved, the results did not conform to the predictions. In 1935, Oppenheimer and Phillips worked out a theory—subsequently known as the Oppenheimer–Phillips process —to explain the results. This theory is still in use today.