Accurate semiempirical potential energy curves for the a3Σ+-state of NaCs, KCs, and RbCs.

Michael Schwarzer,J Peter Toennies

doi:10.1063/5.0046194

Abstract

A five parameter semiempirical Tang-Toennies type model is used to describe the potential curves of the a3Σ+-state of the heteronuclear polar molecules NaCs, KCs, and RbCs. These molecules are of current interest in experiments at ultra-cold conditions to explore the effects of the strong dipole-dipole forces on the collective many-body quantum behavior. New quantum phenomena are also anticipated in systems consisting of atomic species with different fermion/boson statistics. The model parameters are obtained by simultaneously fitting all five of the parameters to the extensive LIF-Fourier transform spectroscopy published by Tiemann and collaborators [e.g., Docenko et al. J. Phys. B: At., Mol. Opt. Phys. 39, S929-S943 (2006)], who also report best fit potential curves. Although the new potentials are in good agreement with the earlier potentials, they have the advantage that they are continuous over the entire range of internuclear distances and have the correct long-range behavior. The scattering lengths for all isotope combinations show good agreement with dedicated experiments where available. The new potentials are also in excellent agreement with combining rules based on the potentials of the homonuclear systems.

Highlights

The laser cooling of alkali atoms to ultralow temperatures of 10−3–10−9 K and the experimental realization of a Bose–Einstein condensate of sodium atoms in 19951 have opened up a vast new field of physics and chemistry research
In the long-range region, both Piecewise Multi-Parameter (PMP)-potentials agree since they are based on the same the dispersion coefficients for C6 and C8; only C10 was increased by 2.5% in Ref. 24
Appendix C demonstrates that with the exception of NaCs, the potential parameters are in good agreement within less than about 0.6% with estimates based on combining rules

Summary

Introduction

The laser cooling of alkali atoms to ultralow temperatures of 10−3–10−9 K and the experimental realization of a Bose–Einstein condensate of sodium atoms in 19951 have opened up a vast new field of physics and chemistry research. For the first time, it is possible to create under controlled conditions macroscopic manybody correlated quantum systems.. Only atom systems were investigated, but laser techniques make it possible to create alkali dimer molecules either in X1Σ+ or in the a3Σ+ ground electronic states. The heteronuclear alkali dimers formed in such mixtures are presently used to explore the effect of the strong anisotropic dipole–dipole forces on the collective correlated behavior at ultralow temperatures. Heteronuclear molecules offer new possibilities to study quantum state selected chemical reactions.

Methods

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Discussion

Conclusion