In February 1936, Pontecorvo left Italy and moved to Paris to work in the laboratory of Irène and Frédéric Joliot-Curie at the Collège de France on a one-year scholarship to study the effects of collisions of neutrons with protons and on the electromagnetic transitions among isomers. During this period, influenced by his cousin, Emilio Sereni, he adopted the ideals of communism to which he remained loyal for the rest of his life. He formed a relationship with Helene Marianne Nordblom, a Swedish woman working in Paris as a nanny. Whether because of his relationship with Marianne, his interesting work on isomers, or the deteriorating political situation in Italy, he turned down an opportunity in 1937 to apply for a tenured position at the University of Rome to stay in Paris.