Structure ofSn120and the Effect of the Pairing Correlation on the Reduction ofE2Transition inSn118andSn120

A new level scheme is proposed for ${\mathrm{Sn}}^{120}$. The levels proposed are the 1.17 Mev, $2^{+}$; 2.20 Mev, $4^{+}$; 2.29 Mev, $5^{-}$; and 2.49 Mev, $7^{-}$ levels, which is concluded from the revision of the order of the cascade transition from the upper levels; the revised order of radiations are 0.20 Mev, $E2\mathrm{}$; 0.09 Mev, $E1\mathrm{}$; 1.03 Mev, $E2\mathrm{}$; and 1.17 Mev, $E2\mathrm{}$. The transition probabilities of the 0.20-and 0.09-Mev gamma rays are also revised as 1.6×${10}^{-3\mathrm{}}$ and 3.5×${10}^{-5\mathrm{}}$ in units of a single-proton transition. A weak cross-over 1.12-Mev $E3\mathrm{}$ transition is observed whose probability is also reduced by the factor of 1.5×${10}^{-1\mathrm{}}$. All the results of the present experiment together with other data are discussed in terms of the theory of Kisslinger and Sorensen. It is shown particularly that the striking reduction of the 0.26-Mev $E2\mathrm{}$ transition in ${\mathrm{Sn}}^{118}$ as well as that of the 0.20-Mev $E2\mathrm{}$ transition in ${\mathrm{Sn}}^{120}$ is explained as a consequence of the pairing correlation.