Search for $\alpha$ + core states in even-even Cr isotopes

Abstract.

The $\alpha$ + core structure is investigated in even-even Cr isotopes from the viewpoint of the local potential model. The comparison of $Q_{\alpha}/A$ values for even-even Cr isotopes and even-even $A = 46, 54, 56, 58$ isobars indicates that ⁴⁶Cr and ⁵⁴Cr are the most favorable even-even Cr isotopes for the $\alpha$ + core configuration. The ground state bands of the two Cr isotopes are calculated through a local $\alpha$ + core potential containing a nuclear term with (1 + Gaussian) $\times$ (W.S. + W.S.³) shape. The calculated spectra give a very good description of most experimental ⁴⁶Cr and ⁵⁴Cr levels, including the $0^{+}$ bandheads. The reduced $\alpha$-widths, rms intercluster separations and B(E2) transition rates are determined for the ground state bands. The calculations reproduce the order of magnitude of the available experimental B(E2) values without using effective charges, indicate that the low-spin members of the ground state bands present a stronger $\alpha$-cluster character, and point out that the ⁴⁶Cr ground state band has a significant degree of $\alpha$-clustering in comparison with ⁴⁴Ti . The volume integral per nucleon pair and rms radius obtained for the $\alpha$ + ⁵⁰Ti potential are consistent with those reported previously in the analysis of $\alpha$ elastic scattering on ⁵⁰Ti.