Determine the isotopic origin (12C vs 13C) of the measured thermal neutron absorption in carbon reported by Bothe and Jensen (1944)

Determine whether the thermal neutron absorption measured in carbon by Walther Bothe and Peter Jensen in their 1944 Zeitschrift für Physik paper arises from 12C or 13C nuclei, thereby attributing the observed absorption cross section to the correct carbon isotope.

Background

Bothe and Jensen measured the diffusion length in electrographite, corrected for ash absorption, and derived a thermal absorption cross section for carbon. In their analysis, they acknowledged an unresolved ambiguity as to which carbon isotope (12C or 13C) accounted for the measured absorption.

Resolving the isotopic attribution is necessary for accurately interpreting historical measurements and for comparing them against modern cross-section data and simulations that distinguish elemental and isotopic contributions.

References

Whether this absorption belongs to the 12C or 13C nucleus cannot be decided for the time being. In the second case, the absorption cross section of the 13C nucleus would be 0.6·10−24 cm2.

— Myths of Nuclear Graphite in World War II, with Original Translations  (2405.20801 - Park et al., 2024) in Appendix, Walther Bothe 1944 excerpt, Section “6. Evaluation and Result”