A table of x-ray levels of radioactive elements is presented. The levels for Tl, Pb, Bi, Th and U were computed by adding term-differences from x-ray emission spectra to some outer level obtainable from optical spectra; those for other elements were carefully interpolated. The energies of certain gamma-rays of Th B·C, Th C″·D, Ra C·C′, Ac B·C and Ac C·C″ are recomputed from the new levels and known beta-ray energies. In the case of Ellis' data, gamma-ray energies obtained from beta-rays ejected from the $K$-shell are brought into excellent agreement with those based on beta-rays from other shells. Energies of secondary electrons of Bi 83 and Po 84, arising in Auger processes and studied by Ellis, agree with those computed from the new levels within the limits of experimental error. This justifies the use of the new levels in computing the energies of Auger lines of other radioactive elements; those of Rd Ac·Ac X, Ac X·An, and Ms ${\mathrm{Th}}_2$·Rd Th are discussed. The transition Pa·Ac gives gamma-rays of energy 347,400 and 359,300 electron volts, hitherto unknown. The beta-ray spectrum of this transition, so far as it is known, is now completely classified, except for one line. The beta-ray spectra of Rd Th·Th X and U${\mathrm{X}}_1$·U${\mathrm{X}}_2$ are produced by nuclear gamma-rays, not by the $K\alpha$-lines of the daughter elements. Evidence is presented for the view that the band at $Hr=2450\mathrm{}$ gauss cm in the spectrum of U${\mathrm{X}}_2$·U II represents the disintegration electrons of U${\mathrm{X}}_2$, and that the group at 1,300,000 electron volts probably represents the secondary electrons. Attention is directed to the frequent occurrence of an energy difference of the order 84,000 to 90,000 electron volts, in gamma-ray spectra and nuclear energy diagrams.

• Received 16 July 1934

DOI:https://doi.org/10.1103/PhysRev.47.107