felt at the 87 Rb atom as a function of the distance with ethane, ethene and MeTS (Figure (a)), and the distance between the 87 Rb atom and ethane, ethene and MeTS as a function of the norm of the electric field felt by the 87 Rb atom (Figure (b)). As can be seen in the plots, MeTS (green curve) has the largest spatially extended E followed by ethene (red curve) and ethane (blue curve) where the strength of the field at short distances is weaker for ethene which reaches a peak around 3.5 Å (Figure (a)). This is confirmed in Figure where an incoming atom would experience the strongest field due to MeTS. Rb-MeTS has the largest dipole moment of the three coat molecules with 87 Rb (Table ). The MP2/def2-TZVP dipole moment magnitudes for the optimised geometries of 87 Rb-MeTS, 87 Rb-ethene and 87 Rb-ethane are, respectively, 3.6794 Debye, 2.3550 Debye and 0.2282 Debye. For all cases the largest component is along the 87 Rb-molecule coordinate. These dipole moment magnitudes are in line with the norm of the electric field for MeTS, ethene and ethane (Figure ).