Neutron diffraction isotopic substitution experiments on liquid n-decane (C10H22) and n-eicosane (C20H42) are described. The intermolecular H-H structure function h(HH)(Q) and the intermolecular H-H correlation function g(HH)(inter)(r) are obtained without recourse to models of the intramolecular structure. The structure of the g(HH)(inter)(r) found at 2.5, 5.0, and 7.0 Angstrom corresponds to different shells in the H-H pair correlation function. In addition, g(HH)(inter)(r)<1 for a considerable range, due to the screening of intermolecular correlations by intramolecular correlations. This "correlation hole" effect is accentuated by extrapolation of the structure functions to the expected infinite wavelength limit, and shows good agreement with values determined from small-angle neutron scattering (SANS) data. All of these features are in good agreement with the results of molecular dynamics simulations for the closely related system C13H28.