Electronic spectra of ND3 in the region of 64 500–73 500 cm−1 and their vibronic assignments

Using a monochromatic VUV beam generated by two-photon resonant sum frequency mixing in a Mg–Kr mixture, we have investigated the electronic transitions of ND3 in the 64 500–73 500 cm−1 region by detecting the fluorescence from the predissociation fragments of ND3 or by detecting the ions produced via VUV+visible resonance enhanced multiphoton ionization (REMPI). Vibronic transitions from the ground state to the 2n, n=7–12 levels of the B̃ 1E″ state are rotationally resolved and the relevant molecular constants are deduced. Two parallel progressions are observed, of which one has been analyzed previously by Douglas [Faraday Discuss. Chem. Soc. 35, 158 (1963)]. We attribute the progression observed by Douglas as transitions to the 2n31 vibronic levels of the B̃ 1E″ state, the other one as transitions to the 2n3141 vibronic levels of the same electronic state. Transitions to the υ2′=0 vibronic level of the previously assigned D̃ 1E″ state have been rotationally resolved and the electronic symmetry of this electronic state is reassigned to E′.