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Two-dipole and three-dipole interaction coefficients of GROUP XII elements

The study of long-range interactions is increasingly becoming essential due to its various applications in cold atomic physics. These interactions can be conveniently expressed in terms of dispersion coefficients. In the present work, theoretical calculations have been carried out to estimate the two-dipole ($C_6$) and three-dipole ($C_9$) dispersion coefficients between the group XII atoms and their ions, \textit{viz.}, Zn, Cd, Hg, Zn$^+$, Cd$^+$, and Hg$^+$. To obtain these coefficients, the dynamic dipole polarizabilities and reduced matrix elements required are evaluated using the relativistic methods for both the considered atoms and ions. Further, using the calculated matrix elements, the oscillator strengths corresponding to leading transitions and static dipole polarizabilities are determined. These are compared with the available values in the literature through which the accuracy of the present calculations ascertains. However, the oscillator strengths for few transitions of Zn, Cd, Hg, Zn$^+$, Cd$^+$, and Hg$^+$, are not reported earlier, and we have provided their values in this work. Thereafter, the dispersion $C_6$ and $C_9$ coefficients are calculated for various combinations of the group XII elements, and most of these coefficients were not reported earlier in the literature. Furthermore, the combinations for which the other theoretical and experimental values were available for comparison showed good agreement. We, therefore, believe that our results reported for $C_6$ and $C_9$ coefficients for various combinations of group XII elements are reliable.