In 1934 Frédéric and Irène Joliot-Curie bombarded aluminium with alpha particles (emitted by polonium) to effect the nuclear reaction  +  →  + , and observed that the product isotope  emits a positron identical to those found in cosmic rays by Carl David Anderson in 1932. This was the first example of  decay (positron emission). The Curies termed the phenomenon "artificial radioactivity", because  is a short-lived nuclide which does not exist in nature. The discovery of artificial radioactivity would be cited when the husband-and-wife team won the Nobel Prize.