Abstract
Measurements of total collision cross sections by means of molecular beams, especially on the scattering of alkali atoms by various gases, arereviewed, and the problems in the measurements are discussed in detail. In this part, the correction terms for the thermal motions of the target gases are calculated and the angular resolution for the detection of the beam deflected into small angles is re-examined theoretically. In addition, the velocity dependence of the total cross sections and the glory effects are discussed.