States of Even-Even Nuclei in the Near-Harmonic Region: Spectra of Rn218, Rn220, and Rn222

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 $\alpha$ emission) of the observed radiations were: ${\mathrm{Ra}}^{222}$: 325 kev (8.4×${10}^{-5\mathrm{}}$), 475 kev (7×${10}^{-5\mathrm{}}$), 525 kev (2×${10}^{-5\mathrm{}}$), and 798 kev (2.5×${10}^{-4\mathrm{}}$); ${\mathrm{Ra}}^{224}$: 290 kev (9×${10}^{-5\mathrm{}}$), 410 kev (4×${10}^{-5\mathrm{}}$), 650 kev (6×${10}^{-5\mathrm{}}$); ${\mathrm{Ra}}^{226}$: 260 kev (0.9×${10}^{-4\mathrm{}}$), 420 kev (7×${10}^{-6\mathrm{}}$, 450 kev (3×${10}^{-6\mathrm{}}$), 610 kev (1.0×${10}^{-5\mathrm{}}$). 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.