RATE CONSTANTS FOR THE REACTION OF AR-2 AND CO AS A FUNCTION OF TEMPERATURE FROM 300 TO 1400 K - DERIVATION OF ROTATIONAL AND VIBRATIONAL-ENERGY EFFECTS( WITH O)

Rate constants for the charge-transfer reactions of Ar+ with O-2 and C O have been measured in a high temperature flowing afterglow from 300 to 1400 K. Comparisons between our results and the previous flow drift tube studies of Dotan and Lindinger at 300 K illustrate the effects o f internal excitation on the reactivity. The rate constants measured f or both systems agree favorably with the drift tube results from 300 t o 900 K. Rotational and translational energy decreases charge transfer equally, consistent with previous experiments, indicating a long-live d collision complex forms during the reaction. The flowing afterglow r ate data deviate from the drift tube results above 900 K as a result o f populating vibrationally excited states of the neutral reagents. Cha rge transfer from the thermally populated spin-orbit excited state of Ar+ with O-2 and CO only slightly enhances the rate constants at 1400 K. Populating the upsilon ''>0 levels reduces the threshold for access ing excited state products, and the rate constants for vibrationally e xcited states are much larger than for upsilon ''=0. The data suggest most of the enhancement comes from upsilon ''>2. (C) 1998 American Ins titute of Physics. [S0021-9606(98)00537-6].