The Natural X-ray Spectrum of Radium B

Extract

It is now well known that radium B is an isotope of lead of atomic number 82 with a mass 214, and consequently, if the atoms of radium B are bombarded by an external source of electrons, the spectrum excited in it should be identical with that of lead atomic number 82. A very interesting question arises with regard to the L radiation emitted by a source of radium B during its spontaneous transformation. At the moment of the expulsion of the disintegration electron from radium B, the internal atomic structure of radium B corresponds to an element of number 82, but an instant later, when the electron has escaped from the nucleus, the charge on the latter is 83 and there must follow a reorganisation of the external electrons. Under these conditions, we cannot be certain whether the L spectrum of radium B should correspond to an element of number 82 or 83. Since the excitation of the L spectrum is for the most part due to the action of the rays from the nucleus, the spectrum should correspond to number 82 if the emission of the γ-ray precedes the escape of the disintegration electron and number 83 if it is subsequent to this process.