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

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

The experimental material on energy levels published from December 1, 1953 to February 1, 1957 is covered along with the 1954 energy level compilation STAP. M. Endt and J. C. Wuyver, Revs. Mod. Phys. 26, 95(1954)!. Little attention is given to cross-section measurements. Many particle reactions, as (n,2n) or spallation reactions, are omitted altogether. Theoretical papers are quoted only briefly. Numerous diagrams and tables and an extensive bibliography are given. (M.H.R.)

Energy Levels of Light Nuclei ( Z = 11 to Z = 20 ). II.

Radioactive atoms: Auger-Electron, α-, β, γ-, and X-Ray Data

Nuclear data sheets for A = 147

The spectral distribution and the total energy of the internal bremsstrahlung of ${\mathrm{P}}^{32}$ were measured from 20 to 1000 kev with a NaI(Tl) scintillation spectrometer. Special care was taken to diminish and correct for bremsstrahlung from the apparatus and the surroundings. The experimental curve agrees with theory from 20 to 50 kev and in the region 50-120 kev shows a weak bump in a smoothed curve; from 120 to 500 kev the curve lies 15 percent, at 800 kev 45 percent, and at 1000 kev 70 percent above a theory based on allowed $\ensuremath{\beta}$ transition; thus, above 120 kev, the experimental curve disagrees with the theory for both allowed and forbidden $\ensuremath{\beta}$ transitions. The total energy per $\ensuremath{\beta}$ decay in the internal bremsstrahlung was found to exceed the calculated value by 21 percent.Using the same experimental arrangements the external bremsstrahlung emitted when the ${\mathrm{P}}^{32}$ $\ensuremath{\beta}$ rays are completely stopped in carbon, aluminum, iron, tin, and lead was also measured. For light elements the observed spectrum was found to agree closely with the theory by Bethe and Heitler as improved by Elwert, but for heavy elements and high energies to exceed the calculated values considerably, e. g., for lead at 500 and 1000 kev by a factor of 1.4 and 2.0, respectively.

Internal and External Bremsstrahlung Accompanying the Beta Rays of P 32

The internal bremsstrahlung, emitted in the $\ensuremath{\beta}$ decay of ${\mathrm{S}}^{35}$, was investigated with a NaI scintillation spectrometer. Neither the shape of the spectral distribution nor the absolute yield was found to agree with theory. At 50 kev the experimental photon yield was 65 percent greater than the theoretical. At 100 kev it was even 180 percent greater. The total photon energy yield per $\ensuremath{\beta}$ decay, 2.23\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$ ${\mathit{mc}}^{2}$, was 35 percent greater than the calculated value.The external bremsstrahlung, emitted when the $\ensuremath{\beta}$ particles from ${\mathrm{S}}^{35}$ were stopped in matter, was also investigated with the same apparatus. With elements of low atomic number the experimental values agreed with those calculated. In experiments using elements of higher atomic numbers, however, the experimental values differed widely from those calculated, the difference increasing with the atomic number. Thus, for lead at 50 kev the experimental value was 60 percent greater than the theoretical, and at 100 kev it was 170 percent greater.

Internal and External Bremsstrahlung in Connection with the Beta Decay of S 35

A NaI(Tl) scintillation spectrometer was used for the study of the spectral distribution of the internal bremsstrahlung from the beta emitters ${\mathrm{Pr}}^{143}$ (${E}_{\ensuremath{\beta}max}=922$ kev) and ${\mathrm{Pm}}^{147}$ (${E}_{\ensuremath{\beta}max}=226$ kev). Both the shape of the corrected experimental spectra and the total yield of internal bremsstrahlung measured per beta decay disagree with the original Knipp-Uhlenbeck theory and with the improved version of this theory, which takes into account the nuclear Coulomb field. For ${\mathrm{Pr}}^{143}$ the measured bremsstrahlung yield exceeds that of the Knipp-Uhlenbeck theory by factors of 1.58 (1.48) and 2.56 (1.50) at 50 and 500 kev, respectively. The numbers in parentheses refer to the Coulomb-corrected theory. The corresponding factors for ${\mathrm{Pm}}^{147}$ are 1.58 (1.37) and 6.1 (2.45) at 25 and 150 kev, respectively.

N. Starfelt

Papers

Internal and External Bremsstrahlung Accompanying the Beta Rays of P 32

Internal and External Bremsstrahlung in Connection with the Beta Decay of S 35

Internal Bremsstrahlung from Pr 143 and Pm 147

The yield of characteristic X-rays excited by β-rays