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Abstract

We study the van der Waals interaction between Rydberg alkali-metal atoms with fine structure (n²L_j; L≤2) and heteronuclear alkali-metal dimers in the ground rovibrational state (X¹Σ⁺; v=0, J=0). We compute the associated C₆ dispersion coefficients of atom-molecule pairs involving ¹³³Cs and ⁸⁵Rb atoms interacting with KRb, LiCs, LiRb, and RbCs molecules. The obtained dispersion coefficients can be accurately fitted to a state-dependent polynomial O(n⁷) over the range of principal quantum numbers 40≤n≤150. For all atom-molecule pairs considered, Rydberg states n²S_j and n²P_j result in attractive 1/R⁶ potentials. In contrast, n²D_j states can give rise to repulsive potentials for specific atom-molecule pairs. The interaction energy at the LeRoy distance approximately scales as n^-5 for n>40. For intermediate values of n≲40, both repulsive and attractive interaction energies of the order of 10–1000μK can be achieved with specific atomic and molecular species. The accuracy of the reported C₆ coefficients is limited by the quality of the atomic quantum defects, with relative errors ΔC₆/C₆ estimated to be no greater than 1% on average.