α:2n:α Molecular Band in ¹⁰Be

The 10.15 MeV resonance in Be-10 has been probed via resonant He-6+He-4 elastic scattering. It is demonstrated that it is the J(pi)=4(+) member of a rotational band built on the 6.18 MeV 0(+) state. A Gamma(alpha) of 0.10-0.13 MeV and Gamma(alpha)/Gamma=0.35-0.46 were deduced. The corresponding reduced alpha width, gamma(alpha)(2), indicates one of the largest alpha-cluster spectroscopic factors known. The deformation of the band, including the 7.54 MeV, 2(+) member, is large (h(2)/2I=200 keV). Such a deformation and the significant degree of clusterization signals a well-developed alpha:2n:alpha molecular structure.