The heavy quark spin symmetry implies that in addition to the recently observed $Z(10610)$ and $Z(10650)$ molecular resonances with $I^G=1^{+}$, there should exist two or four molecular bottomonium-like states with $I^G=1^{-}$. Properties of these $G$-odd states are considered, including their production in the radiative transitions from ${\rm Y}(5S)$, by applying the same symmetry to the ${\rm Y}(5S)$ resonance and the transition amplitudes. The considered radiative processes can provide a realistic option for observing the yet hypothetical states.

• Received 16 June 2011

DOI:https://doi.org/10.1103/PhysRevD.84.031502