In a discharge-pumped F2laser, time-resolved net-small-signal gain has been measured to study the population inversion by employing an oscillator-amplifier configuration. Characteristics of the gain and the fluorescence are studied under various conditions in two cases of He and Ne buffer gases. The peak of the net-small-signal gain in He/F2and Ne/F2show values of about 17&percent;/cm and 9&percent;/cm, respectively. The formation processes of the upper laser level F2(D′) are discussed on the basis of these experimental results. ©1997 American Institute of Physics.