Calculation of rovibrational energy states for water vapor using the symmetric top approximation in the Pade form.
Considering the water vapor molecule for ka > or = J/2 >> 1 as a symmetric top, the simple analytical Pade form for vibrational rotational energy levels was proposed. The rotational spectroscopic parameters for ground and 010 vibrational states of H2O molecule in the framework of this model have been obtained with good prediction. The absorption coefficient of water vapor in the spectral range 725-925 cm(-1) has been calculated for 1000-6000 K temperatures taking into account the transitions to high-excited states up to J < or = 35 and J < or = 30 for the 000 and 010 vibrational states, respectively. It is shown that the prominent role of transitions to high-excited states is in 8-12 microm atmospheric transparency window.
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