Three different isotopic species of CO
2were excited by the output of a line-tunable pulsed HF laser providing about 1 mJ per pulse pump energy. Excited CO
2gases then lased, in a mirrorless system, on six lines in the

m range. Gains in excess of 2 cm
-1and quantum efficiencies close to 50 percent were measured. Two lines, 4.473 and 4.528 μm, were found to have less than 5 dB/km atmospheric attenuation.