Molecular alpha-particle clustering in /sup 218/Ra; dipole collectivity in the vicinity of nuclear shell closures

Evidence for the presence of alpha-particle clustering in /sup 218/Ra comes from a number of observables: binding energy S/sub 2n/, Q/sub ..cap alpha../, E/sub x/(J/sup ..pi../), theta/sub ..cap alpha..//sup 2/ and, F/sub ..cap alpha../. That this clustering is a signature for the new dipole collectivity suggested by Iachello and Jackson follows from observation of simultaneous enhancement of selected E1, E2, and E3 deexcitation transition matrix elements; of these the E1 enhancement is most pronounced as would be expected for dipole collectivity.