In 1930 he went to study at the University of Berlin in Germany. As soon as he arrived in Berlin, he became aware of the Bothe report (博特报告) relating to the emission of a new type of high-energy neutral radiation induced by the bombardment of beryllium with α particles from a radioactive polonium source, which was non-ionizing but even more penetrating than the strongest gamma rays derived from radium. These were (wrongly) presumed to be gamma rays.