Operation of the nitrogen ion laser as an optical regenerative amplifier driven by a master oscillator allows the output to be effectively switched into the blue‐green region of the spectrum. In this work an amplifier containing a dilute plasma of nitrogen ions was pumped by thermolecular charge transfer from He2+produced by an intense e‐beam propagating through several atmospheres pressure of gas mixture. The injection of relatively broadband output from a dye laser oscillator caused the output from the amplifier to switch entirely into the (0,2) vibrational component of theB→Xelectronic transition of N+2at 470.9 nm. An output linewidth of 0.007 nm was achieved together with the early saturation of the laser transition needed for the extraction of power from the amplifier at optimal efficiency.