Abstract
Negative absorption of radio frequency waves is observed near the electron cyclotron harmonics (f=nfc) in weakly ionized plasma. The voltage gains near f=fc and f=2fc are about 7 and 4 dB, respectively. The emissions near f=nfc ascribed to this phenomenon are observed up to n=4 in Xe plasma, up to n=2 in Kr plasma, and only at n=1 in Ar plasma. Their powers are stronger by several tens of dB than those corresponding to thermal noise. The frequency shift from f=nfc as a function of the electron‐neutral collision frequency is measured and compared with the theoretical result where the electron distribution function is assumed to be a δ function.