Predissociation supported high-resolution vacuum ultraviolet absorption spectroscopy of excited electronic states of NH3

Abstract

Using monochromatic vacuum ultraviolet radiation generated by two-photon resonant sum frequency mixing in a Mg–Kr mixture we have investigated the electronic transition of NH3 in the 67 000–73 000 cm−1 region by detecting the fluorescence from the predissociation fragments of NH3. The spectrum is simplified using a pulsed molecular beam. Vibronic bands of the B 1E″ (29, 210, 211, 212, 2731, 2831) state are clearly identified and relevant molecular constants are deduced. The predissociation in the B̃ 1E″ state is found to be nearly independent of the rotational quantum numbers (J,K) within one vibrational band. The linewidths of different vibronic components of the B̃ 1E″ state are measured. In addition, other absorption bands are presented including previously unobserved weak absorption features.