Intracavity Laser Absorption Spectroscopy of D2O between 12 850 and 13 380 cm−1

The high resolution absorption spectrum of dideuterated water, D2O, 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 D2O spectrum. The achieved sensitivity (noise equivalent absorption αmin ∼ 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 D216O 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 D216O transitions is provided as Supplementary Material.