Knowledge Bank

Fourier Transform spectra of $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}NH3$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}NH3$ have been obtained with the multiple reflection White type cell (16 m baselength) at Kitt Peak. The advantage of using long path FTS data over a wide spectral range will be discussed by illustrating some of the results recently obtained for ammonia. These include the possibility of identification of forbidden transitions the extension of assignments in the $\nu 2$ band to higher J quantum numbers and the observation and assignments of many hot bands. These measurements have also made it possible to complete and to correct the assignments of vibration-rotation transitions (up to $J\prime =11-12$) to the energy levels $2\nu 2,\nu 4,\nu 2+\nu 4$ and $3\nu 2$ which have formed the basis for a new analysis of this complex system of interacting levels. The Hamiltonian matrix including all essential perturbations and the numerical model developed will be discussed.