High-Lying Rotational Levels of Water Obtained by FIR Emission Spectroscopy

In an attempt to compute an accurate linelist for the water molecule, the high resolution emission spectrum of water vapor has been recorded between 50 and 600 cm−1 using a Bruker IFS 125HR Fourier transform interferometer and a continuous flow of water vapor rovibrationaly excited by an electrodless radio-frequency discharge. More than 6000 pure rotational lines within the eight first vibrational states were assigned up to J = 35. Rotational as well as rovibrational lines were identified for higher lying states belonging to the first hexad. About 1000 pure rotational transitions within vibrational states of the first hexad were assigned for the first time. The new data, along with a large body of high-resolution data, was fitted using the bending-rotation theoretical approach to compute line positions. In a preliminary analysis, the wavenumbers of 4185 new transitions involving all vibrational states up to the first triad were accounted for up to J = 27 with a root mean square value of 0.87 X 10−3 cm−1. Work is still in progress and we are hoping to account for the new data up to the second triad and beyond. In the paper, the new data will be presented and the results of the line position analysis will be given. The observed minus calculated residuals obtained in the present analysis will be compared to those retrieved using other calculated or experimental rovibrational energies.