Abstract
Measurements of NH3 absorption coefficients are presented for several transitions of a C13O216 laser for small concentrations of NH3 (p ≤ 1 Torr) for absorption lines broadened to 1 atm with N2. NH3 absorption coefficients were determined for laser transitions R(8) (920.2194 cm−1) to R(28) (933.8808 cm−1) of the 00°1 − [10°0,02°0]I band. The strongest absorption coefficient [K = 36.09 ± 1.43 (atm-cm)−1] was measured for the R(18) transition for the NH3 line, aQ(6,6), and is larger than has been found in any previous measurements with a CO2 laser. The dependence of K on total pressure was also obtained for select transitions, and the frequency separation between the R(18) laser transition and the neighboring NH3 line [aQ(6,6)] was determined to be 550 ± 50 MHz. These results are significant for long path absorption monitoring of NH3 with CO2 lasers since the path length can be reduced by approximately 40% and for heterodyne detection of NH3 since the relative position of the laser transition to the NH3 absorption line is well within the bandpass of Hg–Cd–Te photomixers (B ≥ 1.5 GHz).
© 1975 Optical Society of America
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