Gamma-Ray Intensities in the Thorium Active Deposit

The relative intensities of the gamma rays of the descendants of radiothorium have been studied by measuring the photoelectron spectra from thorium and platinum foils. The relative sensitivity of the arrangement at different energies was found by using other sources having gamma rays of known relative intensity. Comparison of the measured gamma-ray intensities with the measurements by others of internal conversion intensities allows internal conversion coefficients to be computed and the multipolarities of several transitions to be determined. An electric monopole transition was found in ${\mathrm{Po}}^{212}$. The gamma-ray intensities are used to find the intensities of beta-ray branches. Gamma-ray intensities are compared with the known intensities of long-range alpha particles from ${\mathrm{Po}}^{212}$ and transition probabilities are estimated for some electromagnetic transitions between states of that nucleus. The level schemes of ${\mathrm{Po}}^{212}$ and ${\mathrm{Pb}}^{208}$ are discussed in the light of the information found here and of other recent information.