A table is presented of a complete list of the radioactive and stable isotopes, with a number of their salient features, as recorded in the literature or by private communications up to February 1958. (W.D.M.)

Table of isotopes

Energy levels of Z = 11−21 nuclei (IV)

Energy levels of A = 21−44 nuclei (V)

Energy levels of light nuclei. III Z = 11 to Z = 20

Energy Levels of Light Nuclei. V

Radioactivity Produced by Proton Bombardment of Bromine and Iodine

On the basis of simple theoretical considerations it is expected that short-lived positron emitters should be produced in fluorine, sodium, and magnesium under bombardment with 6-Mev protons. These activities have been found and ascribed to ${\mathrm{Ne}}^{19}$, ${\mathrm{Mg}}^{23}$, and ${\mathrm{Al}}^{25,\phantom{\rule{0ex}{0ex}}26}$. Half-lives, positron spectra and threshold investigations have been made and found to compare very well with the theory. It is concluded that for isobars of the type $(n\ensuremath{-}p)=\ifmmode\pm\else\textpm\fi{}1$ the difference in binding energy is due solely to the effect of Coulomb forces up to at least mass number 25. The half-lives are found to depend on the inverse fifth power of the upper limit of the positron spectra in agreement with the theory.

Short-Lived Radioactivities Induced in Fluorine, Sodium and Magnesium by High Energy Protons

Four nuclei of the type discussed by Wigner, containing one more proton than neutron, have been produced. The nuclei, their half-lives and positron energies are: ${\mathrm{P}}^{29}$, 4.6 seconds, 3.63 Mev; ${S}^{31}$, 3.2 seconds, 3.85 Mev; ${\mathrm{Cl}}^{33}$, 2.4 seconds, 4.13 Mev; and ${\mathrm{A}}^{35}$, 2.2 seconds, 4.38 Mev. These energies are in excellent agreement with the calculated values and indicate that (1) the $\ensuremath{\pi}\ensuremath{-}\ensuremath{\pi}$ force is equal to the $\ensuremath{\nu}\ensuremath{-}\ensuremath{\nu}$ force plus the Coulomb repulsion, (2) the nuclear volumes are proportional to the atomic weights, and (3) the nuclear charge is distributed uniformly through the volume. The half-life-energy relation is in good agreement with the Fermi theory. Deviations are in the direction anticipated by the Gamow-Teller modification.

Positrons from Light Nuclei

The Carbon Isotopes of Mass Ten and Eleven

The absorption of water and dehydration of these films is found to obey a diffusion equation by means of which a diffusivity may be defined. This is not a constant but depends on the water concentration in the foils. A rapid change in water content immediately after changing the ambient conditions suggests the presence of adsorbed surface layers. The total absorption is found to increase faster than the relative humidity.

E. C. Creutz

Papers

Radioactivity Produced by Proton Bombardment of Bromine and Iodine

Short-Lived Radioactivities Induced in Fluorine, Sodium and Magnesium by High Energy Protons

Positrons from Light Nuclei

The Carbon Isotopes of Mass Ten and Eleven

Absorption of Water by Films of Cellophane and Polyvinyl Alcohol