Neutron Compton-Scattering From Amorphous Hydrogenated Carbon

Neutron Compton scattering (NCS) measurements have been used to determine the kinetic energies of atoms in samples of amorphous hydrogenated carbon (a-C:H), graphite and diamond at momentum transfers between 40 and 300 Angstrom(-1). We find that the kinetic energy of individual carbon atoms is the same within statistical error in a-C:H and graphite but significantly higher in diamond. The kinetic energy of the hydrogen in a-C:H is lower than expected from previous spectroscopic measurements and we infer that the sample contained molecular hydrogen. Observed deviations from the impulse approximation are consistent with theoretical calculations. We discuss future prospects for Ncs measurements on non-crystalline materials.