It has long been recognised that paraffin (C n H 2n+2 where n > 20) is a good coat molecule for magnetometer cell walls. Alternative coat molecules to paraffin include alkyl chains terminated with the functional group trichlorosilane (organochlorosilanes) and monounsaturated alkene chains. Ulanski and Wu measured dwell times of spin polarized rubidium-87 atoms on pentacontane (CH 3 (CH 2 ) 48 CH 3 ) and octadecyltrichlorosilane (OTS) coated surfaces. They used the Larmor frequency shift of 87 Rb to determine, at 72 • C, the dwell times in OTS-coated cells as 0.9 µs and in paraffin-coated cells as 1.8 µs. The dwell time for OTS is shorter than that for paraffin, whereas the relaxation probability for OTS is larger than that for paraffin by almost one order of magnitude: paraffin-coated surfaces can support 10,000 polarization-preserving collisions with spin-polarised Rb atoms; 7 in contrast OTS-coated surfaces can support 1,000 collisions. They concluded that the superior anti-relaxation property of paraffin is not due to an extremely short dwell time of spin polarized 87 Rb atoms in paraffin-coated cells, but due to the average strength of the interactions experienced by the atoms while they are inside paraffin-coated cells, which are much weaker than while they are inside OTS-coated cells.