“…The theoretical investigations by Gervais' group in Caen has shown that in alkali (A)-rare gas (RG) pairs, the spin-orbit coupling depends strongly on the alkali-rare gas distance R A−RG . 8,9 The effect is especially large when a light alkali atom (e.g., Na) interacts with a heavy rare gas (e.g., Xe). For instance, considering the energy levels, which correlate with the first 2 P state of the alkali atom at infinite R A−RG separation, the molecular spin-orbit coefficients a(R NaÀXe ) ¼ h 2 Π 1=2 jH SO j 2 Π 1=2 i and b(R NaÀXe ) ¼ h 2 Π À1=2 jH SO j 2 Σ 1=2 i of the Na-Xe pair, vary from +5.7 cm −1 at infinite Na-Xe separation to +27.5 and −21.1 cm −1 , respectively, when R Na−Xe = 3.4 Å.…”