A chance encounter and discussion with Niels Bohr's assistant in a café in Copenhagen led him to abandon his thesis on ancient languages and to commence studies in nuclear physics.
After studying in Copenhagen and Berlin, he joined Curie's Institut du Radium in Paris in 1923, following Bohr's recommendation.
[4] In 1929, he used the electromagnet of the Académie des sciences, under the direction of Aimé Cotton, to study the a radiation of thorium C (now known to be bismuth-212).
[1] He continued his research with the electromagnet, at the time the most powerful in the world, studying the radiation of other radioactive elements (such as actinium in 1929, using a specimen prepared by Curie herself).
He worked at the École libre des hautes études, a 'university-in-exile' chartered by the French and Belgian governments-in-exile for their refugee academics.