Low-Lying Negative-Parity Bands of $^{152}$Sm via Deuteron Inelastic Scattering

Nuclei near N=90 and Z=64 have recently been suggested to be `tetrahedral-magic' [1]. One of the main signatures for tetrahedral symmetry is a vanishing quadrupole moment in low-lying negative-parity bands. This has the consequence that a rotational band possess very weak, or even vanishing, E2 matrix elements. With N=90 and Z=62, $^{152}$Sm is a potential candidate for relatively stable tetrahedral symmetry. Complementing studies of $^{156}$Dy [2], the structure of $^{152}$Sm has been investigated using deuteron inelastic scattering with a 22 MeV polarized deuterium beam at the MP tandem Van de Graaff accelerator of the TU/LMU Munich. The deuterons from the reaction were momentum analyzed using the Q3D spectrometer. Absolute cross sections and analyzing powers have been extracted for levels up to 2 MeV. The low-lying negative-parity bands are observed to be strongly populated, however detailed coupled-channel calculations are required before transition elements can be extracted due to the many possible population pathways. Details of the experiment and analysis will be presented. [1] J. Dudek et al., PRL \textbf{88}, 25 (2002). [2] D.J. Hartley et al., Bull. APS \textbf{54}, 10 (2009).