Decay ofFm253

Abstract

The decay scheme of ${\mathrm{Fm}}^{253}$ has been investigated by $\alpha$-particle, $\gamma$-ray, and electron spectroscopy. Eleven $\alpha$ groups were observed with energies and intensities 7.092(1.3%), 7.032(6.7%), 6.952(42.7%), 6.910(9.8%), ∼6.876(∼0.9%), 6,855(8.4%), 6.682(23.2%), 6.659(2.4%), 6.639(2.6%); 6.550(1.5%), and ∼6.496 MeV (∼0.3%). Two $\gamma$ rays of energy 144.8 and 271.8 keV were identified and their multipolarities determined as $M2\mathrm{}$ and $E2\mathrm{}$, respectively. The excited state at 144.8 keV has been assigned as $\frac{5}{2}+$ (622↑) and the half-life of this level was measured to be 45 μsec. The level at 416.6 keV is identified as the ½+ (620↑) state. The energy levels of ${\mathrm{Cf}}^{249}$ and the $\alpha$ transition probabilities to them seem to be in agreement with the current theories.