Low Temperature Physics: 45, 715 (2019); https://doi.org/10.1063/1.5111294
The role of spin-orbit coupling in the optical spectroscopy of atomic sodium isolated in solid xenon
P. de Pujo1*, M. Ryan2, C. Crépin3, J.-M. Mestdagh1, and J.G. McCaffrey2
1Laboratoire Interactions, Dynamiques et Lasers (LIDyL) CEA, CNRS and Université Paris-Saclay — UMR 9222 CEA Saclay F-91191 Gif-sur-Yvette, France
2Department of Chemistry, National University of Ireland — Maynooth, Maynooth, County Kildare, Ireland
3Institut des Sciences Moléculaires d’Orsay (ISMO), UMR 8214, CNRS, Univ. Paris-Sud, Université Paris-Saclay, F-91405 Orsay Cedex, France
Received January 17, 2019, published online May 28, 2019
Molecular dynamics calculations, based on the diatomics-in-molecules method, have been used to probe the manifestations of spin-orbit (SO) coupling in the experimental absorption bands of atomic sodium isolated in solid xenon. Inclusion of SO coupling of –320 cm−1 in spectral simulations of the 3p 2P ← 3s 2S transition leads to unequal band spacings which very closely match the asymmetrical bandshape observed for blue single vacancy (SV) site occupancy. This SO value, extracted in a previous MCD study, reveals the dramatic change in the effective SO coupling constant of the Na atom (from the gas phase value of +17 cm−1) in solid Xe when it is close to the 12 xenon atoms in the first surrounding sphere. In contrast, the symmetrical three-fold split band of the red tetra vacancy (TV) site in Na/Xe is not affected nearly as much by SO coupling. This reflects a greatly reduced “external heavy atom” effect when the 24 Xe atoms surrounding the Na atom in TV are located at great-er distances. The contrasting behavior of sodium in the SV and TV sites suggests a strong dependence of the SO coupling strength on the Na–Xe distance.
Key words: spin-orbit coupling, atomic sodium, solid xenon, blue single vacancy, red tetra vacancy.