Knowledge Bank

Doppler limited absorption spectra of the vibration-rotation transitions of $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}N18O$ and other isotopic species have bean recorded in the fundamental region using a tunable diode source and a 1 meter base length multiple traversal cell. The spectra show both Lambda-type doubling and nuclear magnetic hyperfine splitting of the rotational energy levels. Satellite band transitions ($\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2-2\Pi 3/2$ and - $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 3/2-2\Pi 1/2$) as well as main band transitions ($\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2-2\Pi 1/2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 3/2-2\Pi 3/2$) in the ground electronic states were recorded. These new data combined with similar quality data obtained for the normal isotopic species will provide the necessary data for unique determination of the $A(\nu )$ constant a as well as Lambda-type doubling parameters. The hyperfine and Lambda doubling data are in good agreement with previously published microwave data and theory.