Electron drift velocities have been measured in binary gas mixtures using the Bradbury-Nielsen method. The data have significant advantages over those for the pure gases in analyses to obtain electron scattering cross sections. The first study was carried out to make a more definitive test of the threshold region of the v = 0->1 vibrational excitation cross section for hydrogen than was possible previously using electron drift velocity data for hydrogen-argon and hydrogen-helium mixtures. The

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... xtures used were 1.160 % hydrogen -98.84 % neon and 2.892 % hydrogen -97.11 % neon at 294 K and electron drift velocities were obtained with an estimated uncertainty of < ± 0.5 % at values of E /N from 0.12 to 1.7 Td. These measurements are highly sensitive to the region of the threshold of the v = 0->1 vibrational excitation cross section for hydrogen. The theoretical v = 0->1 vibrational excitation cross section of Morrison et al. (1987) is shown to be incompatible with the present measurements. A new set of hydrogen cross sections has been derived from the available electron swarm measurements in pure hydrogen