Electric quadrupole moment of the $4d ^{2}D_{5/2}$ state in   $^{88}Sr^{+}$ and its role in an optical frequency standard
  The electric quadrupole moment for the $4d ^2D_{5/2}$ state of $\mathrm{^{88}Sr^+}$, one of the most important candidates for an optical clock, has been calculated using the relativistic coupled-cluster theory. The result of the calculation is presented and the important many-body contributions are highlighted. The calculated electric quadrupole moment is $(2.94\pm0.07)ea_{0}^{2}$, where $a_{0}$ is the Bohr radius and $e$ the electronic charge while the measured value is $(2.6\pm0.3)ea_{0}^{2}$. This is so far the most accurate determination of the electric quadrupole moment for the above mentioned state. 
Chiranjib Sur, K. V. P. Latha, Rajat K. Chaudhuri, B. P. Das and D.   Mukherjee