-Disintegration and the Sargent Diagram

Sargent diagrams constructed for negative-electron-active species having 80< Z <94 (as also for the restricted group with 80< Z <84), and for both negative-electron-active and positron-active species having Z <22, are discussed in the light of theory. The majority of first-forbidden transitions in the group of heaviest radioelements give a Sargent line parallel to the allowed line, corresponding to disintegration constants smaller by a factor of roughly 10 only than the disintegration constants of allowed transitions of equal energy. Transitions with no parity change between states of zero spin appear to give a second-forbidden line also parallel to the allowed line. With the lightest radioelements "super-allowed" transitions are identified which require Wigner selection rules for their interpretation, but there is also a group of transitions which appears to be ordinarily allowed (i.e. subject to spin and parity selection rules only). Compared with these allowed transitions in the lightest elements, allowed transitions in the heaviest radioelements are less probable by a factor of about three only, when comparison is made for equal energy release and account is taken of the effect of the coulomb field of the nucleus. On the assumption that all (even, even) nuclei have even parity and zero spin in the ground state it is concluded that the β-particles of maximum energy observed with RaB, RaC and MsTh 1 are emitted in transitions to excited states of the final nuclei RaC, RaC' and MsTh 2 , respectively. This conclusion makes it likely that the accepted value of the total γ-ray emission from RaB (Gray 1937) is too small, that the total disintegration energy Ra.C.C' is 3.78 MeV. and that MsTh 1 emits a low-energy γradiation which has not as yet been detected. On the same assumption it is concluded that the disintegrations UX 1 .UX 2 and UX 2 . U 11 possess features at present unknown or insufficiently understood.