Exotic Molecular States in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow/><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">Be</mml:mi></mml:math>

The breakup of ${}^{12}\mathrm{Be}$ into ${}^{6}\mathrm{He}{+}^{6}\mathrm{He}$ and ${}^{4}\mathrm{He}{+}^{8}\mathrm{He}$ has been studied using a 378 MeV ${}^{12}\mathrm{Be}$ beam inelastically excited by ${}^{12}\mathrm{C}$ and $({\mathrm{CH}}_{2}{)}_{n}$ targets. The measurements indicate that breakup occurs from rotational states in the 10 to 25 MeV excitation energy interval, with spins in the range of $4\ensuremath{\Elzxh}$ to $8\ensuremath{\Elzxh}$. The inferred moment of inertia is consistent with the cluster decay of an exotic molecular structure in ${}^{12}\mathrm{Be}$, which may be associated with an $\ensuremath{\alpha}\ensuremath{-}4n\ensuremath{-}\ensuremath{\alpha}$ cluster configuration.