Measurement and analysis of new terahertz and far-infrared spectra of high temperature water

Terahertz absorption spectroscopy and far infrared Fourier transform (FIR-FT) emission spectroscopy were employed to measure new rotational and ro-vibrational spectra and validate existing datasets for high temperature water, with the goal to improve the accuracy of predictions for pure rotation in the (0 2 0), (1 0 0) and (0 0 1) vibrational states. A total of 104 new rotational transitions in (0 0 0), (0 1 0), (0 2 0), (1 0 0) and (0 0 1) were observed in the 293-2723 GHz region with MW accuracy and with observed J(Max) = 18, 11, 10, 14, 10; Ka(Max) = 10, 7, 7, 7, 4; E″(Max) = 4178, 3771, 4996, 5430, 4939 cm−1, respectively. A total of 4194 new FIR-FT transitions were assigned in the 50-600 cm−1 region to the same five vibrational states with estimated experimental uncertainty of 0.0008-0.002 cm−1 and with J(Max) = 27; Ka(Max) = 21, 18, 18, 17, 17, respectively. Together with previous high-resolution observations, these new data were fitted with the Bending-Rotation approach and the Euler Hamiltonian. The new measurements and predictions reported here will support the analyses of astronomical observations by high-resolution spectroscopy telescopes such as Herschel, SOFIA, and ALMA.

Highlights► Terahertz absorption and FT-FIR emission spectroscopy of high temperature water. ► 104 new THz lines assigned for (0 0 0), (0 1 0), (0 2 0), (1 0 0), (0 0 1). ► 4194 new FT-FIR lines assigned for the same five states (accuracy: 0.0008-0.002 cm−1). ► J up to 27 fitted to experimental accuracy.