Journal of Physics B Atomic Molecular and Optical Physics

Accurate analytical potential energy curves for the a 3 Σ + state of LiK, LiRb and LiCs

Dongying Li, Xiaowei Sheng

Published Jul 14, 2026• 0 citations

Abstract

Abstract Heteronuclear lithium-containing alkali dimers in their ground triplet state offer both electric and magnetic dipole moments, which arise from their unpaired electron distributions and make them suitable for exploring many-body quantum phenomena. Currently, no simple yet accurate analytical form exists to model the triplet interaction potentials of heavier Li-alkali pairs such as LiK, LiRb and LiCs. The Sheng-Tang–Toennies(STT) potential, containing merely two fitting parameters, has earlier successfully reproduced the lowest triplet potential curve of Li 2 and LiNa. In this work, we extend its application to predict the a 3 Σ + state interactions for the three dimers LiK, LiRb, and LiCs. The derived analytical potentials agree closely with high-level a b i n i t i o benchmarks and existing spectroscopic measurements over the complete range of internuclear separations. Our findings verify the robustness and portability of the STT model for representing triplet state potentials across heteronuclear alkali dimers that include lithium.

DOI: 10.1088/1361-6455/ae8a96

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Journal of Physics B Atomic Molecular and Optical Physics

Accurate analytical potential energy curves for the a 3 Σ + state of LiK, LiRb and LiCs

Dongying Li, Xiaowei Sheng

Published Jul 14, 2026• 0 citations

Publisher

Abstract

DOI: 10.1088/1361-6455/ae8a96

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arXiv:1912.01568Physical Review AMar 23, 20206 citations

We study the van der Waals interaction between Rydberg alkali-metal atoms with fine structure (

{n}^{2}{L}_{j}

; $L\ensuremath{\le}2$) and heteronuclear alkali-metal dimers in the ground rovibrational state ($X^{1}\mathrm{\ensuremath{\Sigma}}^{+}$;

v=0, J=0

). We compute the associated

{C}_{6}

dispersion coefficients of atom-molecule pairs involving

^{133}\mathrm{Cs}

and

^{85}\mathrm{Rb}

atoms interacting with KRb, LiCs, LiRb, and RbCs molecules. The obtained dispersion coefficients can be accurately fitted to a state-dependent polynomial

O({n}^{7})

over the range of principal quantum numbers $40\ensuremath{\le}n\ensuremath{\le}150$. For all atom-molecule pairs considered, Rydberg states

n^{2}S_{j}

and

n^{2}P_{j}

result in attractive

1/{R}^{6}

potentials. In contrast,

n^{2}D_{j}

states can give rise to repulsive potentials for specific atom-molecule pairs. The interaction energy at the LeRoy distance approximately scales as ${n}^{\ensuremath{-}5}$ for

n>40

. For intermediate values of $n\ensuremath{\lesssim}40$, both repulsive and attractive interaction energies of the order of 10--$1000\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{K}$ can be achieved with specific atomic and molecular species. The accuracy of the reported

{C}_{6}

coefficients is limited by the quality of the atomic quantum defects, with relative errors $\mathrm{\ensuremath{\Delta}}{C}_{6}/{C}_{6}$ estimated to be no greater than 1% on average.