On the uncertainty of the calculated intensities of the water vapor lines in the sub-THz frequency range
R.I. Ovsyannikov, M.Yu. Tretyakov, M.A. Koshelev, T.A. Galanina
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Nizhny Novgorod, Russia
Keywords: line intensity, water molecule, subTHz, atmospheric absorption
Abstract
The comparative analysis of data available from open sources on the water spectral lines intensities in the frequency range from 0 to 1.75 THz has been carried out. The calculations by the method of effective Hamiltonians and the variational method, as well as experimental data were taken into account. It has been established that the intensity uncertainty is less than 2% for lines in the ground vibrational state with an intensity of more than 10-27 cm/mol. and is about 5-10% for weaker lines. For strong (more than 10-26 cm/mol.) lines in the ν2 state, the uncertainty ranges from 2 to 5% and increases to 5-10% for weak lines. For all lines in the 2ν2, ν1, and ν3 states, the uncertainty is no more than 5-10%. The presented data show that most of the considered lines can be assigned a higher (by 1-2 steps according to the classification adopted in HITRAN) category of intensity accuracy.
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