Intracavity Laser Absorption Spectroscopy of D 2O between 12 850 and 13 380 cm −1

Abstract

The high resolution absorption spectrum of dideuterated water, D 2O, has been recorded by Intracavity Laser Absorption Spectroscopy (ICLAS) in the 12 850–13 380 cm −1 spectral region which is the higher energy region reported so far for this water isotopologue. Very high deuterium enrichment was necessary to minimize the HDO absorption lines overlapping the D 2O spectrum. The achieved sensitivity (noise equivalent absorption α min ∼ 10 −9 cm −1) allowed detecting transitions with line strengths on the order of 5 × 10 −28 cm/molecule. The spectrum analysis, based on recent variational calculations has provided a set of 422 new rovibrational energy levels belonging to 11 vibrational states, including rotational sublevels for four new vibrational states and one level of the (0 9 1) highly excited bending state. The very weak (1 0 4)–(0 0 0) band at 13 263.902 cm −1, which is the highest D 2 16O band currently observed, could be assigned despite the fact that the HDO absorption in the region is stronger by three orders of magnitude. The list of 996 D 2 16O transitions is provided as Supplementary Material.