An apparatus to measure precise total differential cross sections of electrons scattered by gases employing an electron counting system

The apparatus is described in detail, and compared with existing units. Its high precision possibilities are discussed. A sample experiment was performed using CO 2 and 30 keV electrons; the total scattered intensities are presented for the range of s from 0.45 AA -1 to 32 AA -1 , where s is the classical electron diffraction parameter. The normalisation technique is discussed; and the results are compared with previously published measurements. The difference function obtained by comparison with the predictions of the independent atom model shows doubly shaped oscillations, which are not due to experimental error.