New energy levels for $^{157}$ Sm

This work is based on analysis of $\gamma$-$\gamma$-$\gamma$ and $\gamma$-$\gamma$-$\gamma$-$\gamma$ coincidence data from the observation of prompt $\gamma$-rays emitted in the $^{252}$Cf spontaneous fission with Gammasphere at Lawrence-Berkeley National Lab. An extended new level structure of $^{157}$Sm is proposed in part based upon systematics of adjacent $^{155}$Sm and $^{159}$Sm. A comparison of the three isotopes will be presented. The proposed new $^{157}$Sm structure incorporates 21 new transitions and 12 new levels and shifts 5 of the previously determined transitions to higher spin values.