Abstract
An apparatus has been constructed to measure the total cross section for electron scattering by atoms and molecules. It can be viewed as a linearisation of the Ramsauer technique, with a well defined solid angle for the analyser/collector. The effective length of the absorbing gas cell used in the transmission measurement could be determined accurately by comparing the results obtained with two cells of different length. Measurements on He and N2 have been carried out for 15-750 eV electrons with an accuracy of 4% or better. The results are compared with existing experimental and theoretical data from other groups. The data for He link up within the experimental uncertainty with some recent theoretical calculations below the inelastic threshold and agree very well in the overlapping energy region with the recent experimental data of Kennerly and Bonham (see Rev. Sci. Instrum., vol.48, p.822 (1977)).