A remeasurement of the 2³S excitation cross section in helium

The classical experiment of Maier-Leibnitz has been repeated. Corrections have been applied for secondary electron emission from mesh and collector electrodes resulting from the incidence of metastable helium atoms, for the finite permeability of the mesh to electrons and for the value of retarding potential between mesh and collector. Random walk calculations have been used to determine the mean number of elastic collisions made by an electron in traversing the apparatus. The value obtained at the maximum of the 2 3 S cross section is 2.6 × 10 -18 cm 2 ± 17%, indicating that the error in the original determination (3.7 × 10 -18 cm 2 ± 20%) was underestimated.