The influence of the 126-neutron shell on the alpha-decay properties of the isotopes of emanation, francium, and radium

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Abstract

A consideration of alpha systematics indicated that it might be possible to prepare a number of new isotopes of emanation, francium, and radium with half-lives sufficiently long to permit radio-chemical isolation and identification. These isotopes were predicted to lie below the neutron number 126, or much lighter in mass number than the naturally occurring isotopes of these elements. The new isotopes were looked for and found in various cyclotron bombardments, including the bombardment of thorium with high-energy protons, the bombardment of lead with high-energy carbon ions, and bombardment of gold with high-energy nitrogen ions. Data are presented for 16-hour Em211, 2·7-hour Em210, 30-minute Em209, 23-minute Em208, 11-minute Em207, 6·2-minute Em206, 2·7-minute Ra213, and 19-minute Fr212. The complete data are summarized in Table 2.

The methods of chemical purification, the measurements of the energy of the radiations, and the experiments proving genetic relationships are discussed in detail. Of particular interest is the development of a glow-discharge method for the deposition of rare-gas radioactivity on metallic counting foils.

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    This work was carried out under the auspices of the U.S. Atomic Energy Commission.

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