RESONANT CHARGE TRANSFER CROSS SECTIONS OF ATOMIC AND POLYATOMIC IONIC SPECIES FROM MOBILITY DATA E. Basurto, J. de Urquijo, I. Alvarez, and C. Cisneros Centro de Ciencias F=EDsicas, UNAM, P.O. Box 48-3, 62251 Cuernavaca, Mor.,= MEXICO The mobility of He+, Ne+, Ar+, N2+, O2+, and CO2+ in their parent gas was measured over a wide range of the density-normalised electric field intensity, E/N, with a double mass spectrometer-drift tube apparatus. The mobilities were used to derive the resonant charge transfer cross sections which, for the case of the monoatomic species, agree well with previously published data in the overlap range.=20