The fluorescence excitation spectrum of deuterated ammonia in the region 105–200 nm: the states of ND₃

The fluorescence excitation spectrum of a molecular beam of ND3 has been measured in the spectral region 105–200 nm using synchrotron radiation. The thresholds for the formation of ND (b and c) are found to be the same at 124 ± 1 nm, indicating that ND (b) is formed by cascading from ND (c) and is not a primary photoproduct. A vibrational band analysis for the states of ND3 has been performed yielding values for the vibrational frequencies of the bending mode for the excited states of 720, 749 and 794 cm-1, respectively. There are large violet isotopic zero band shifts between NH3 and ND3 for these states (-247, -281 and -114 cm-1, respectively).