ORIENTATION OF MOLECULARLY INTERCALATED N-2 IN C24K

The nuclear-resonance photon-scattering technique was used to study the tilt angle of physisorbed N2 with respect to the graphene planes Of C24K prepared from highly oriented pyrolytic graphite. This was done by measuring the ratio of the resonantly scattered intensities from the 6324-keV level in N-15 with the photon beam parallel and perpendicular to the graphene planes. In the temperature range T = 10-190 K where nitrogen is molecularly intercalated into the C24K, a huge anisotropy, a factor almost-equal-to 2.5, was observed in the scattering cross sections. This is interpreted in terms of the orientation of the molecular axes of the N2 molecules as being very nearly parallel to the graphene planes. Above 200 K, the amount of molecularly intercalated N2 was negligible.