Quadrupolar contact terms and hyperfine structure

In the interaction of two electric quadrupoles, there is at short range a contact term proportional to the second derivative of a δ function. This contact term contributes to the hyperfine splitting of bound states of two particles with spin one or higher -- for example, the bound state of Ω- and a nucleus with spin one. The contact hyperfine splitting occurs in states with orbital angular momentum unity (P wave), in contrast to the Fermi contact interaction, which is in S states. We find that these contact splittings will be observable with Ω- atoms and help measure the quadrupole moment and charge radius of the hyperon