In 1934, Frédéric and Irène Joliot-Curie bombarded aluminium with alpha particles to effect the nuclear reaction 2 He + 13 Al → 15 P + 0 n, and observed that the product isotope 15 P emits a positron identical to those found in cosmic rays (discovered by Carl David Anderson in 1932). This was the first example of β decay (positron emission), which they termed artificial radioactivity since 15 P is a short-lived nuclide which does not exist in nature. In recognition of their discovery, the couple were awarded the Nobel Prize in Chemistry in 1935.