Submillimeter Emission from Optically Pumped ¹⁴NH₃

A CO 2 TEA laser was used for optical pumping of 14 NH 3 . Thirteen CO 2 lines, which deviate by 0.05 cm -1 or less from transitions in 14 NH 3 , were effective in producing submillimeter laser transitions. Most of the 24 emitted lines have wavelengths between 70 and 400 μm and represent rotation-inversion transitions in the ν 2 state of NH 3 . A few short wavelength lines (30-70 μm) are 2ν 2 transitions obtained by pumping from the ν 2 state. The influence of pressure, resonator length and outcoupling on the appearance of the submillimeter lines was investigated. The choice of parameters was not critical for observing the lines, which in general had high gain. Each pump pulse delivered 1-50 mJ in 150 ns to the NH 3 gas. Some submillimeter lines persisted up to an NH 3 pressure of 30-70 torr or to 300-400 torr in a mixture of NH 3 and He.