Hyperfine structure splitting of the ground states in the $pd\mu, pt\mu$   and $dt\mu$ ions
  The hyperfine structure splittings of the ground states of the $pd\mu, pt\mu$ and $dt\mu$ ions are determined with the use of highly accurate expectation values of the interparticle delta-functions obtained in recent computations. The corresponding hyperfine structure splittings, e.g., $\Delta_{12} =$ 1.3400149$\cdot 10^7$ $MHz$ and $\Delta_{23} =$ 3.3518984$\cdot 10^7$ $MHz$ for the $pt\mu$ ion, can directly be measured in modern experiments. 
ALexei M. Frolov
physics.atom-ph nucl-th