Measurements of NH_3 absorption coefficients with a C^13O_2^16 laser

Measurements of NH(3) absorption coefficients are presented for several transitions of a C(13)O(2)(16) laser for small concentrations of NH(3) (p </= 1 Torr) for absorption lines broadened to 1 atm with N(2). NH(3) absorption coefficients were determined for laser transitions R(8) (920.2194 cm(-1)) to R(28) (933.8808 cm(-1)) of the 00 degrees 1 - [10 degrees 0,02 degrees 0](I) band. The strongest absorption coefficient [K = 36.09 +/- 1.43 (atm-cm)(-1)] was measured for the R(18) transition for the NH(3) line, aQ(6,6), and is larger than has been found in any previous measurements with a CO(2) 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 NH(3) line [aQ(6,6)] was determined to be 550 +/- 50 MHz. These results are significant for long path absorption monitoring of NH(3) with CO(2) lasers since the path length can be reduced by approximately 40% and for heterodyne mdetection of NH(3) since the relative position of the laser transition to the NH(3) absorption line is well within the bandpass of Hg-Cd-Te photomixers (B >/= 1.5 GHz).