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Dual Decay of Potassium

1943; Nature Portfolio; Volume: 152; Issue: 3847 Linguagem: Inglês

10.1038/152103a0

1476-4687

F. Christian Thompson, Sam Rowlands,

X-ray Spectroscopy and Fluorescence Analysis

IT has been known for some time that the?-ray activity shown by potassium is due entirely to the isotope 40K, which thereby transforms to 40Ca. One might expect that 40K would exhibit a dual decay, transforming to 40A either by emission of a positron or by the electron-capture process. Attempts have been made at various times to detect positrons in the radiation from potassium but without success. These experiments, however, would not have detected the electron-capture process. In 1937, von Weizsäcker pointed out that considerations of the abundance of the chemical elements suggested that the isotope 40K may in fact transform by a capture process to 40A. The argument was as follows. The abundance of the chemical elements varies on the whole smoothly with atomic number, and the inert gases as a class show the same variation, except that they are rarer by several powers of 10 than their neighbouring elements. Argon is a striking exception, for it is about 1,000 times more abundant than would be expected from the general rule. The excess is due entirely to 40A, and argon would obey the rule if the 40A atoms could be attributed entirely to the transformation of 40K.