Electron Correlation Effects in Hyperfine Interactions in $^{45}$Sc and   $^{89}$Y
  The relativistic coupled-cluster theory has been employed to calculate the magnetic dipole and electric quadrupole hyperfine structure constants for the stable isotopes $^{45}$Sc and $^{89}$Y. The role of electron correlation is found to be very important. The trend exhibited by these effects is rather different from previously studied single valence atomic systems. 
Bijaya K. Sahoo, Thomas Beier, B. P. Das, R. K. Chaudhuri and Debashis   Mukherjee