Parity Measurements Using the Polarized (d, α) Reaction Near 0º

Abstract

<p>A new model-independent method is presented for determining certain spectroscopic information in odd-odd nuclei. It uses the (d, α) reaction with a polarized deuteron beam incident on a spin-zero target nucleus and with the alpha particles detected near 0º to the beam direction. By measuring the tensor analyzing power for the reaction to a particular final state, it is possible to determine whether that state has natural parity or unnatural parity. In addition, the method allows spin-zero levels in the final nucleus to be uniquely identified and the tensor polarization of the beam to be measured. The fluctuations of the tensor analyzing power with energy for unnatural parity states are calculated using the statistical compound nucleus model and it is shown that, for most cases, an average of the cross-sections for three energies will be sufficient for unambiguously assigning natural parity or 0‾ to a level. It has also been shown that the expected attenuation of the tensor analyzing power for natural parity states is negligible when the alpha particles are detected near 0º.</p> <p>This method is applied to the reactions 12C(d,α)10B, 16O(d,α)14N, and 40Ca(d,α)38K, resulting in many new spin and parity assignments. In particular, assignments of J^π = 0‾ are made to the 4.91 MeV level and to one member of the doublet at 9.13 MeV in 14N. Assignments of 3‾, (2,4)‾, 2‾, (2‾,3+), 2‾, 1+, and 1+ are made to the 2613, 2647, 2870, 3317, 3815, 3857, and 3978 keV states, respectively, of 38K.</p> <p>The results of a shell-model calculation of the negative parity T = 0 states in 38K are presented.</p>