The aim is to establish the nature of the surface layer of 8CB at the nematic-air interface by measuring neutron reflection from the n=8, 10 and 12 homologues of the nCB series of liquid crystals. For each homologue, two differently deuterated versions will be used. This system has been chosen because nematic-air is the simplest possible homeotropic nematic surface and so represents the baseline for future studies of homeotropic alignment agents for devices. There has been a suggestion that the first layer of 8CB is not the normal smecticAd arrangement. Comparison between the two isotopomers will establish the validity of deductions in terms of molecular ordering. The variation along the homologgous series will also test current theories of the surface smectic wetting at temperatures above the smectic transition.