Nuclear structure of manganese-56

The Mn55(d, p)Mn56 reaction was investigated with 10-keV resolution at a deuteron bombarding energy of 7.5 MeV. Angular distributions were obtained for most states up to 5.5 MeV and for strong states up to about 6.5 MeV of excitation energy. A distorted-wave (DW) analysis yielded the orbital angular momentum transfer ln and the transition strength (2Jf+1) Slj for most states. A comparison with the (d, p) sum rules gives evidence that the DW calculations may be accurate to about 20%. Considerable configuration mixing between the 2p32, 2p12, and 1f52 neutron orbitals was found. A discussion of possible spin assignments is given, particularly for states below 1 MeV. The statistical model is found to be reasonably consistent with the present data, but the distribution of nearest-neighbor spacings has some features of a Wigner, and not an exponential, distribution. Shell-model calculations are discussed, and the possibility that Mn56 may have a large static deformation is considered.