Deviations from Born-Oppenheimer mass scaling in spectroscopy and ultracold molecular physics

Lutz, J.J.; Hutson, J.M.

Abstract

We investigate Born-Oppenheimer breakdown (BOB) effects (beyond the usual mass scaling) for the electronic ground states of a series of homonuclear and heteronuclear alkali-metal diatoms, together with the Sr2 and Yb2 diatomics. Several widely available electronic structure software packages are used to calculate the leading contributions to the total isotope shift for commonly occurring isotopologs of each species. Computed quantities include diagonal Born-Oppenheimer corrections (mass shifts) and isotopic field shifts. Mass shifts dominate for light nuclei up to and including K, but field shifts contribute significantly for Rb and Sr and are dominant for Yb. We compare the ab initio mass-shift functions for Li2, LiK and LiRb with spectroscopically derived ground-state BOB functions from the literature. We find good agreement in the values of the functions for LiK and LiRb at their equilibrium geometries, but significant disagreement with the shapes of the functions for all 3 systems.The differences may be due to contributions of nonadiabatic terms to the empirical BOB functions. We present a semiclassical model for the effect of BOB corrections on the binding energies of near-threshold states and the positions of zero-energy Feshbach resonances.

Citation

Lutz, J., & Hutson, J. (2016). Deviations from Born-Oppenheimer mass scaling in spectroscopy and ultracold molecular physics. Journal of Molecular Spectroscopy, 330, 43-56. https://doi.org/10.1016/j.jms.2016.08.007

• Journal Article Type: Article
• Acceptance Date: Aug 14, 2016
• Online Publication Date: Aug 17, 2016
• Publication Date: 2016-12
• Deposit Date: Aug 9, 2016
• Publicly Available Date: Sep 7, 2016
• Journal: Journal of Molecular Spectroscopy
• Print ISSN: 0022-2852
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 330
• Pages: 43-56
• DOI: https://doi.org/10.1016/j.jms.2016.08.007
• Related Public URLs: https://arXiv.org/abs/1608.02141