Hot NH3 Spectra for Astrophysical Applications

Abstract

We present line lists for ammonia (NH$_{3}$) at high temperatures obtained by recording Fourier transform infrared emission spectra. Calibrated line lists are presented for twelve temperatures (300 -- 1300$^{\circ}$C in 100$^{\circ}$C intervals and 1370$^{\circ}$C) and each line list covers the 740 -- 2100 cm$^{-1}$ range, which includes the majority of the $\nu_{2}$ umbrella bending mode region (11 $\mu$m) and the $\nu_{4}$ asymmetric bending mode region (6.2 $\mu$m). We also demonstrate the useful technique of obtaining empirical lower state energies from a set of spectra recorded at different sample temperatures. Using our NH$_{3}$ spectra, we have estimated lower state energies ($E_{Low}$ in cm$^{-1}$) and our values have been incorporated into the line lists along with calibrated wavenumbers ($\tilde{\nu}$ in cm$^{-1}$) and calibrated line intensities ($S'$ in cm/molecule) for each line. We expect our hot NH$_{3}$ line lists to find direct application in the modelling of planetary atmospheres and brown dwarfs.