Letter | Published:

Spacing of the Resonance Neutron Levels of Silver, Rhodium and Bromine Nuclei

Nature volume 140, pages 768769 (30 October 1937) | Download Citation



FROM recent work on group and thermal neutrons1, the constants describing the resonance absorption of an element can be calculated fairly accurately. This simplifies the estimation of the average spacing of the resonance neutron levels in the experiment of Chao and Fu2 and makes it possible to work with a thinner paraffin scatterer so as to obtain a beam of neutrons distributed more uniformly over the energy spectrum. We have now made measurements with a paraffin scatterer of only 2 mm. thickness. The neutron source consisted of 100 mgm. radium surrounded with 12 gm. beryllium, and the scatterer in the form of a spherical shell was of 4 cm. outer diameter. Detectors of silver, rhodium and bromine, approximately 3 cm. × 3 cm. in size, were exposed at a distance of 1·2 cm. from the paraffin, and the induced activity was measured with a Geiger-Müller counter.

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  1. 1.

    and , Phys. Rev., 50, 899 (1936); and , Phys. Rev., 50, 328 (1936); and , Phys. Rev., 49, 519 (1936); and , Phys. Rev., 51, 450 (1937).

  2. 2.

    and , Chinese J. of Phys., 2, 135 (1936); NATURE, 139, 325 (1937).

  3. 3.

    This formula can be obtained from formula (12) of the paper in Chinese J. of Phys. by neglecting the long factor.

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  1. Physics Department, Tsing Hua University, Peiping. July 27.

    • C. Y. CHAO
    •  & T. H. WANG


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