Disintegration Scheme ofRa226(1620 yr)

Abstract

The excited states of ${\mathrm{Em}}^{222}$ were studied in connection with a survey of regularities in heavy even-even nuclei. ${\mathrm{Em}}^{222}$ was shown to have a second excited state of character 2+, 4+, or possibly 0+ at 448 kev. This result was obtained by confirming the existence of a weak $\gamma$ ray of 260 kev in the ${\mathrm{Ra}}^{226}$ spectrum, which had previously been observed by Stephens in coincidence with ${\mathrm{Ra}}^{226}$ $\alpha$ rays. This $\gamma$ ray was found to be in coincidence with the well-known 188-kev transition leading from the first excited state (2+) to the ground state. The intensity ratio $I_{\gamma 260}:I_{\gamma 188}=1:400\mathrm{}$. From this ratio and the known value of 5.7% for the $\alpha$ branch feeding the 188-kev state, the intensity of the $\alpha$ branch feeding the 448-kev state was found to be ∼0.01%.