High-Resolution Absorption Spectroscopy of ND ₃ between 59,000 and 93,000 cm –¹

Complementing our recent work on ammonia [Pratt et al., J. Mol. Spectrosc. 2023, 396, 111810], we here present new high-resolution photoabsorption spectra of deuterated ammonia, ND 3, spanning the region between 59,000 and 93,000 cm –1 . This region extends from just above the Franck–Condon envelope for the A ̃ 1 A 2 ″ ← X ̃ 1 A 1 ′ transition to well above the ND 3 + X ̃ + 2 A 2 ″ ionization threshold. The absolute photoabsorption cross sections were recorded at room temperature using the Fourier transform spectrometer at the Synchrotron SOLEIL with a measured spectral resolution of 0.22 cm –1, which is a factor of 10–100 times higher than in any previously reported broadband spectrum of ND 3 . The spectra reveal partially resolved rotational structure in several different vibrational progressions, which allows the reassignment of some of the higher energy bands, enabling proposed assignments for the P1 and P2 progressions reported by Wu et al. [ J. Chem. Phys . 2007, 127, 154311] and an expanded appraisal of the pattern of lower-lying Rydberg states of ammonia.