The 10.15 MeV resonance in 10Be has been probed via resonant 6He+4He elastic scattering. It is demonstrated that it is the Jpi=4+ member of a rotational band built on the 6.18 MeV 0+ state. A Gammaalpha of 0.10-0.13 MeV and Gammaalpha/Gamma=0.35-0.46 were deduced. The corresponding reduced alpha width, gamma2alpha, indicates one of the largest alpha-cluster spectroscopic factors known. The deformation of the band, including the 7.54 MeV, 2+ member, is large (h2/2I=200 keV). Such a deformation and the significant degree of clusterization signals a well-developed alpha:2n:alpha molecular structure.

The breaking of the N=8 shell-model magic number in the 12Be ground state has been determined to include significant occupancy of the intruder d-wave orbital. This is in marked contrast with all other N=8 isotones, both more and less exotic than 12Be. The occupancies of the [FORMULA: SEE TEXT]orbital and the [FORMULA: SEE TEXT], intruder orbital were deduced from a measurement of neutron removal from a high-energy 12Be beam leading to bound and unbound states in 11Be.

The very neutron-rich oxygen isotopes 25

An experiment was performed at the Australian National University to study the 9 Be( 6 Li, 6 Li) 9 Be * → α + α + n reaction. This experiment was designed to study the breakup of 9 Be, in an attempt to quantify the contribution played by the 5 He + α and 8 Be 2 + + n channels for the low lying excited states. This information is required in order to resolve uncertainties in the α + α + n → 9 Be reaction rate in high-energy and neutron-rich astrophysical environments such as supernovae. Angular correlation measurements have been used to deduce that the 2.429 MeV state breaks up almost exclusively via the 8 Be 2 + channel. This method of identifying the break-up channel resolves the problem of distinguishing between the 8 Be 2 + and 5 He g.s. channels which are kinetically identical at this excitation energy.

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