Hot NH3 Spectra for Astrophysical Applications

TL;DR

This paper provides high-temperature ammonia spectral line lists derived from Fourier transform infrared emission spectra, useful for modeling planetary atmospheres and brown dwarfs, with empirical lower state energies included.

Contribution

The study presents calibrated, high-temperature NH3 line lists covering 740-2100 cm$^{-1}$, including empirical lower state energies, for astrophysical applications.

Findings

Line lists for 12 temperatures from 300°C to 1370°C.

Coverage of key vibrational modes relevant to astrophysics.

Inclusion of empirically derived lower state energies.

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.