Irène Joliot-Curie
The difficulty of making the measurement is illustrated by the wide-ranging values for the mass of the neutron obtained from 1932 to 1934. The accepted value today is . In Chadwick's 1932 paper reporting on the discovery, he estimated the mass of the neutron to be between and . By bombarding boron with alpha particles, Frédéric and Irène Joliot-Curie obtained a high value of , while Ernest Lawrence's team at the University of California measured the small value using their new cyclotron.