Vanishing spin alignment : experimental indication of triaxial ${}^{\mathbf{28}}\mathbf{S}\mathbf{i}+{}^{\mathbf{28}}\mathbf{S}\mathbf{i}$ nuclear molecule

Fragment-fragment-$\gamma$ coincidences have been measured for $\rm ^{28}Si + {^{28}Si}$ at an energy corresponding to the population of a conjectured resonance in ${}^{56}$Ni. Fragment angular distributions as well as $\gamma$-ray angular correlations indicate that the spin orientations of the outgoing fragments are perpendicular to the orbital angular momentum. This differs from the ${}^{24}\mathrm{M}\mathrm{g}+{}^{24}\mathrm{M}\mathrm{g}$ and the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ resonances, and suggests two oblate ${}^{28}\mathrm{S}\mathrm{i}$ nuclei interacting in an equator-to-equator molecular configuration.