α∶2n∶αMolecular Band inBe10

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