Evidence for shape coexistence in 151Eu

Although the ground states of ¹⁵¹Eu and ¹⁵³Eu both have $\text{I}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{+}}$, the (p, t) transition connecting these states is extremely weak. A level at 261 keV with a large (p, t) cross section is assigned as the deformed $\text{5}\text{2}{}^{\mathrm{+}}$[413] state in the “spherical” nucleus ¹⁵¹Eu.