Parity Measurements Obtained from the ⁴⁸Ca(đ,α)⁴⁶K

Abstract

<p>A polarized deuteron beam was used to initiate a (d,α) reaction on an even-even target with the detection of the reaction products near 0°. A model independent technique is utilized which allows the parity of a nuclear state (natural or unnatural) to be determined from a measurement of the tensor analyzing power T₂₀. In addition, it is possible to identify 0¯ levels uniquely.</p> <p>This reaction was performed on a doubly-magic ⁴⁸Ca target. The resulting isotope ⁴⁶K may therefore be treated as a proton hole and a neutron hole in a ⁴⁸Ca core. As a result of this simple shell-model picture, several investigations into the spins and parities of the low-lying states of ⁴⁶K have been conducted. However, some of these model dependent assignments have yielded contradictory results - hence the need for this study.</p> <p>The ⁴⁸Ca(đ,α)⁴⁶K reaction was carried out at 4° with bombarding energies of 7.5, 8.0, 8.5, and 9.0 MeV. For a given beam energy, spectra obtained with the incident deuterons preferentially polarized in the m=0 substate were compared with spectra obtained with polarized deuterons in the m=1 substate. The following parities were deduced from the levels in ⁴⁶K: ground state, 0.69, 1.74, °1.94 MeV levels (unnatural parity) 0.59 and 0.89 MeV levels (natural parity). In addition, a tentative natural parity assignment was made to the 1.37 MeV state. The resulting spin-parity combinations are found to be consistent with the most recent set of measurements by Daehnick et.al.².</p> <p>Pandya calculations were made in which the order and separation of the lowest levels of ⁴⁰K were obtained from the ⁴⁶K levels. As a result of configuration mixing, the calculations bear little resemblance to the experimental ⁴⁰K spectrum. A discussion of configuration mixing effects is also provided.</p>