Direct mea
surements of the kinetic energy of Ne atoms adsorbed on activated carbon (AC) at
submonolayer coverage, is reported. The electronvolt spectrometer of the ISIS neutron source that utilizes the neutron Compton scattering technique, was employed. The specific adsorption area of the AC was
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GIF>3000 m<
sup>2
sup>/g. The momentum distribution of adsorbed Neon was mea
sured at 12 K. The kinetic energy of Ne was found to be
66.3±6.2 K, and is much higher than that of solid neon, at the same temperature, being
45.8±4.8 K. This re
sult is considered to be an evidence for the occurrence of a confinement effect of Ne atoms within the pores of the AC. The re
sult was also used for deducing the average pore size of the AC adsorber as
sumed to have slit shaped pores.