Working in collaboration with the French physicist André Lazard at Joliot-Curie's laboratory at Ivry-sur-Seine, Pontecorvo discovered what Frédéric Joliot-Curie called "nuclear phosphorescence"; the emission of X-rays when neutrons and protons were excited and returned to their ground state. He also discovered that some isomers do not change into other elements on decaying radioactively. This expanded the scope for their use in medical applications. For this ground-breaking research, Pontecorvo received a Curie-Carnegie scholarship, and funding for his work from the French National Centre for Scientific Research.