States of Even-Even Nuclei in the Near-Harmonic Region: Spectra ofRn218,Rn220, andRn222

Abstract

Gamma-ray singles and coincidence spectra have been measured in the alpha decay of ${\mathrm{Ra}}^{222}$, and ${\mathrm{Ra}}^{224}$, and ${\mathrm{Ra}}^{226}$. Excluding the prominent transitions from the first excited states, the energies (and abundances relative to total $\ensuremath{\alpha}$ emission) of the observed radiations were: ${\mathrm{Ra}}^{222}$: 325 kev (8.4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$), 475 kev (7\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$), 525 kev (2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$), and 798 kev (2.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$); ${\mathrm{Ra}}^{224}$: 290 kev (9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$), 410 kev (4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$), 650 kev (6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$); ${\mathrm{Ra}}^{226}$: 260 kev (0.9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$), 420 kev (7\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$, 450 kev (3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$), 610 kev (1.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$). The observed gamma-gamma coincidences were ${\mathrm{Ra}}^{222}$: 325-325 kev, 325-475 kev, and 325-525 kev; ${\mathrm{Ra}}^{224}$: 241-290 kev and 241-410 kev; ${\mathrm{Ra}}^{226}$: 188-260 kev and 188-420 kev. It was not strictly determined that the ${\mathrm{Ra}}^{222}$ radiations were not due to other members of the ${\mathrm{Th}}^{226}$ family. These data have been used to deduce the following levels, spins, and parities in the daughter Rn nuclides: ${\mathrm{Rn}}^{218}$: 650 kev, 2+; 800 kev, 1-; and, possibly, 850 kev, 4+. ${\mathrm{Rn}}^{220}$: 530 kev, 2+; and 650 kev, 1-. ${\mathrm{Rn}}^{222}$: 448 kev 2+; and 610 kev, 1-. The 2+ states in ${\mathrm{Rn}}^{220}$ and ${\mathrm{Rn}}^{222}$ have been previously assigned by Scharff-Goldhaber. These results are incorporated in a general energy level systematics of even-even nuclei in the heavy element region.