Abstract
The rovibronic absorption lines shapes of the predissociated à ← X̃ transition of NH3 and ND3 are analyzed. All of the observed features in the room temperature and jet‐cooled absorption spectra are fit by a single Franck–Condon progression in ν2 with systematically varying linewidths. The N–H equilibrium bond length is determined to be 1.08 Å. Vibronic lifetimes of ND3 and NH3 are compared and consequences for the mechanism of photodissociation are discussed.