Correction of differential cross sections for finite angular resolution

The angular resolution of a differential scattering apparatus of the common type is investigated. The primary and scattered beam are each assumed to be non-parallel and collimated by two arbitrary rectangular apertures. A function eta ( theta , Theta ) describing the acceptance of the apparatus for particles scattered at laboratory angle theta is derived, which connects the directly measurable angular distribution dN/d Theta with the differential cross section sigma ( theta ). The two cases of a gas cell target and a locally defined target such as an atomic or molecular beam are both treated.