The B 1E″ state of ammonia: Sub-Doppler spectroscopy at vacuum ultraviolet energies

Spectra of the 2n0 progression in the B̃ 1E″–X̃ 1A′1 transition in NH3 and ND3 have been recorded at an effective resolution down to 0.008 cm−1 at the VUV equivalent energy. Line shape analysis reveals a predissociation lifetime of 0.25(2) ns for ND3 and 6.1(7) ps for NH3 independent of rotational state and v2. Measurement of the magnetic sensitivity of low J lines gave an electronic g value. Rotational analyses of the 2n0 bands with n up to 6 for ND3 and 8 in NH3 are presented and indicate some small vibrational perturbations. The observed difference between the Coriolis coupling constant ζ derived from the rotational structure and the g value indicates a mild Jahn–Teller effect.