Orientation of molecularly intercalated N₂ 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 ¹⁵N 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 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.