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. Second World War Escape from France In June 1939, Pontecorvo applied for a visa to visit Sweden, but his application was rejected. On 23 August came the news of the Molotov–Ribbentrop Pact. He joined the French Communist Party the next day as an affirmation of his personal faith in the Soviet Union. Marianne rejoined him in Paris on 6 September 1939, three days after the British and French declaration of war on Germany in response to the German invasion of Poland that started the Second World War in Europe. They were married on 9 January 1940. As the Germans closed in on the city in May 1940, they decided to leave. Although the British offered refuge to French nuclear scientists, including Hans von Halban and Lew Kowarski, they regarded Pontecorvo as an "undesirable". Fortunately, Segrè had been given an offer of employment in Tulsa, Oklahoma, by two European expatriates who were looking for an expert on neutron physics. Segrè had turned down the offer — he already had a good job at the University of California — but recommended Pontecorvo. On 2 June 1940, he saw Marianne and Gil off with their chattels on a train to Toulouse, where his sister Giuliana lived with her husband, Duccio Tabet. On 13 June, just a day before the Germans entered Paris, Pontecorvo, his brother Gillo, cousin Emilio Sereni and Salvador Luria set out for Toulouse on bicycles. It took them ten days to reach Toulouse. Luria went to Marseilles, from whence he eventually made his way to the United States. Pontecorvo, Marianna, Gil, Giuliana and Tabet boarded a train that took them to Lisbon via Madrid on 19 July 1940. Both women were pregnant. Marianne had a miscarriage, and was hardly fit to travel, but nonetheless boarded the liner Quanza on 9 August 1940 on its voyage bringing refugees to the United States. Both women were seasick. On 19 August 1940, the ship reached New York City, where they stayed with his brother Paolo. While there, he visited Fermi at his new home in Leonia, New