In Section 4.9 of Linus Pauling's General Chemistry Book (Dover 1988 edition, a copy of the WH Freeman and Company 1970 edition) he describes the principle behind the determination of nuclidic mass by nuclear reaction, giving the following beta decay reaction as an example for the determination of the mass of $\ce{{}^{40}_{19}K_{21}}$:

$$\ce{{}^{40}_{19}K_{21} -> {}^{40}_{20}Ca_{20}^+ + e^-}$$

I was wondering if nuclidic masses determined this way remain state of the art (the origin of the currently accepted value of the mass) for any nuclides? More generally, how important is the technique currently?

  • 1
    $\begingroup$ The canonical source for masses, the Atomic Mass Evaluation 2020 part 2 (iopscience.iop.org/article/10.1088/1674-1137/abddaf) shows in column 5 of Table I ("The 2020 Atomic mass table") the 'origin' of the evaluated mass, and many indicate using various decay paths. Interestingly, the example above is not one of them... $\endgroup$
    – Jon Custer
    Jan 13, 2023 at 17:05
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    $\begingroup$ I would expect, considering broad electron-antineutrino energy spectrum, that beta decay would not be the best way for precise measurements. $\endgroup$
    – Poutnik
    Jan 13, 2023 at 19:14
  • $\begingroup$ @Poutnik - sure, for measuring a single decay. You measure a bunch and get the full electron energy spectrum and you have a quite reasonably precise measure. Yes, the alpha channel will be more precise with less data. $\endgroup$
    – Jon Custer
    Jan 13, 2023 at 20:07


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