THE VUV SPECTROSCOPY OF DEUTERATED HYDRAZINE, N2D4

The VUV absorption spectrum of N2D4 has been measured in the spectral region 1050-2100 angstrom using synchrotron radiation. The spectrum, which is largely unstructured. gradually rises from a threshold of 2630 angstrom and is dominated by three broad peaks of increasing magnitude at almost-equal-to 1940, 1685 and 1400 angstrom followed by a drop in the absorption at almost-equal-to 1340 angstrom and then a monotonic rise to the low-wavelength experimental cutoff at 1050 angstrom. The spectrum can be interpreted either in terms of Rydberg excitations of the nonbonding nitrogen electrons with the broad features resulting from spectral congestion or alternatively, the broad nature of the spectrum may be due to absorption of molecular valence states involving sigma* <-- n and sigma* <-- sigma-transitions. Mulliken proposed the existence of such valence transitions by analogy with corresponding features in the isoelectric diatomic halogen molecules.