Each emission of an alpha or beta ray accompanies the transmutation of an atom; the energy communicated to these rays comes from inside the atom.
The time necessary for the disappearance of half the atoms, called the half-life, is a fundamental characteristic of each radio-element; according to the substance, the value of the half-life varies between a fraction of a second and millions of years.
We have shown that it is possible to create a radioactivity characterized by the emission of positive or negative electrons in boron and magnesium by bombardment with alpha rays.
It was at the beginning of 1934 while working on the emission of these positive electrons that we noticed a fundamental difference between that transmutation and all the others so far produced; all the reactions of nuclear chemistry induced were instantaneous phenomena, explosions.
