Capture Cross-sections for 220 Kev. Neutrons


THE selectivities (in Z) observed in the activation of nuclei by capture of slow neutrons are explained by differences of the energy (E) of the lowest neutron resonance level in different nuclei: the contribution of one level to the capture cross-section for thermal neutrons is proportional to 1/E2, while the cross-section at resonance is proportional to 1√E ; the measured values of E lie between 1 and 200 volts. The application of the one-level formula1,2 to the experimental results yields some evidence on the neutron width n and the radiation width r of the best-known resonance levels. Some experimental evidence on the total widths has also been obtained3,4,5.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Breit and Wigner, Phys. Rev., 49, 519 (1936).

  2. 2

    Bethe and Placzek, Phys. Rev., 51, 450 (1937).

  3. 3

    Amaldi and Fermi, Phys. Rev., 50, 899 (1936).

  4. 4

    von Halban and Preiswerk, J. de Phys. et Rod., 8, 29 (1937).

  5. 5

    von Halban and Paxton, NATURE, 141, 116 (1938).

  6. 6

    Booth and Hurst, Proc. Roy. Soc., A, 161, 248 (1937).

  7. 7

    Reddeman, Naturwiss., 26, 124 (1938).

  8. 8

    Amaldi, Hafstad and Tuve, Phys. Rev., 51, 896 (1937).

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

VON HALBAN, H., KOWARSKI, L. Capture Cross-sections for 220 Kev. Neutrons. Nature 142, 392–393 (1938).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.