In 1934, Frédéric and Irène Joliot-Curie bombarded aluminium with alpha particles to effect the nuclear reaction  +  →  + , and observed that the product isotope  emits a positron identical to those found in cosmic rays (discovered by Carl David Anderson in 1932). This was the first example of  decay (positron emission), which they termed artificial radioactivity since  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.
The theory of electron capture was first discussed by Gian-Carlo Wick in a 1934 paper, and then developed by Hideki Yukawa and others. K-electron capture was first observed in 1937 by Luis Alvarez, in the nuclide V. Alvarez went on to study electron capture in Ga and other nuclides.