Abstract
The ion-ion recombination rate in laboratory air at atmospheric pressure and room temperature has been re-investigated experimentally. Both pulsed and continuous irradiation methods were used. The pulsed source enabled the recombination coefficient to be measured as a function of ion age between ½ msec and ½ sec. It has been shown that the very high initial recombination rates at low ion ages can be satisfactorily explained by the existence of microscopic regions in which the ion density is much higher than the average density over the ionized volume. Decreases in the recombination coefficient which were observed in a few cases at about 50 msec ion age have been attributed to changes in the type of ions involved. Day-to-day variations in the recombination coefficient were ascribed to variations in the minor constituents of the air used. The results of pulsed and continuous methods for recombination coefficient are in quantitative agreement yielding a value of 1·4×10−6 cm3 sec−1 for untreated laboratory air. Although the air used was not necessarily representative of other laboratory environments, this value shows that for much practical work a recombination coefficient considerably lower than that reported in the literature for carefully dried air should be used.