Orientation of molecularly intercalated N2 in C24K.

The nuclear-resonance photon-scattering technique was used to study the tilt angle of physisorbed ${\mathrm{N}}_{2}$ with respect to the graphene planes of ${\mathrm{C}}_{24}$K prepared from highly oriented pyrolytic graphite. This was done by measuring the ratio of the resonantly scattered intensities from the 6324-keV level in $^{15}\mathrm{N}$ with the photon beam parallel and perpendicular to the graphene planes. In the temperature range T=10\char21{}190 K where nitrogen is molecularly intercalated into the ${\mathrm{C}}_{24}$K, a huge anisotropy, a factor \ensuremath{\approxeq}2.5, was observed in the scattering cross sections. This is interpreted in terms of the orientation of the molecular axes of the ${\mathrm{N}}_{2}$ molecules as being very nearly parallel to the graphene planes. Above 200 K, the amount of molecularly intercalated ${\mathrm{N}}_{2}$ was negligible.