Many high-gain lines in the heavy noble gases have been observed in the spectral region from

. Most of the observed lines did not compete and it was possible to obtain simultaneous oscillation at a wide variety of wavelengths in the infrared using a relatively simple pulsed laser apparatus. It is believed that six of the laser lines observed in krypton and argon have not been reported. The new lines are at 0.7603 μ (Kr), 3.708 μ (Ar), 3.774 μ(Kr), 3.957 μ (Kr), 4.069 μ (Kr), and 4.142 μ (Kr). The laser apparatus used in these experiments may readily be used to construct laboratory lasers as convenient frequency standards in the infrared.