Knowledge Bank

The frequencies of 32 obsorption lines of $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}NH3$ in the 9 and 10 micrometer region were measured by use of a diode laser heterodyne spectrometer. The frequencies of 11 additional IR transitions were determined from these measured transitions by forming combination differences with measured inversion and rotation-inversion transitions [1]. The precision of our measurement was about 3 MHz or $1\times 10-4cm-1$. When referred to previous measurements by other ultra-high resolution techniques on 12 lines that have been reported accurate to $2\times 10-4cm-1$ or better, our corresponding measurements have a standard deviation of $1.1\times 10-4cm-1$. After an allowance for systematic errors, we believe our measurements to be accurate to 6 MHz. When referred to our new measurements, the standard deviation of the frequencies of 19 transitions previously measured by etalon calibration is $6\times 10-3cm-1$.