Ba^+ Quadrupole Polarizabilities: Theory versus Experiment

Three different measurements have been reported for the ground state quadrupole polarizability in the singly ionized barium (Ba$^+$) which disagree with each other. Our calculation of this quantity using the relativistic coupled-cluster method disagrees with two of the experimental values and is within the error bars of the other. We discuss the issues related to the accuracy of our calculations and emphasize the need for further experiments to measure the quadrupole polarizability for this state and/or the 5D states.