Experimental determination of the atomic quadrupole moment of graphite

The symmetry of the graphite crystal implies that each carbon atom has an electric quadrupole moment associated with it. This atomic moment may have a significant influence on the location of adsorbed molecules on a graphite surface and on the adsorption energy. A novel experiment, involving the measurement of the effect of a laboratory electric field gradient on the period of oscillation of a small single crystal of graphite mounted on a glass torsion fibre, has been carried out. The quadrupole moment of a carbon atom within the sample is found to be (–3.03 ± 0.10)× 10–40 C m2; however, this value may include a contribution from surface effects.