THE INFLUENCE OF MULTIPLE-SCATTERING PROCESSES ON THE ELECTRON-MOBILITY IN LOW-DENSITY METHANOL GAS

The electron drift mobility mu has been measured in CH3OH gas in the t emperature range 303 less than or equal to T less than or equal to 363 K and in the number density range 2.4 x 10(17) less than or equal to n less than or equal to 2.1 x 10(19) cm(-3). It is usually assumed-alt hough there is no foundation for it-that at such low gas densities the ''zero-field'' density-normalized mobility (mu n) does not depend on n, i.e. it can be described by the so-called Lorentz single collision approximation [see, e.g., N. Gee and G. R. Freeman, Can. J. Chem. 61, 1664 (1983)]. We observed, however, a density dependence of (mu n) whi ch can be explained approximately in terms of coherent and incoherent multiple scattering corrections where the coherent contribution due to correlations between the scatterers predominates at lower temperature s. (C) 1996 American Institute of Physics.