Modeling of Collision-Induced Absorption Spectra of H tex2html_wrap_inline18 -H tex2html_wrap_inline18 Pairs for the Planetary Atmospheres Structure: The Second Overtone Band

Y. Fu, A. Borysow (MTU,USA/NBIfAFG,DK)

Collision induced absorption (CIA) is known to constitute the major component of the opacity of outer planets. The work is of interest for modeling the atmospheres of Uranus and Neptune. The spectra, centred around .83 tex2html_wrap_inline22 m, correspond to the rotovibrational (RV) CIA in the second overtone band (3-0) of H tex2html_wrap_inline18 -H tex2html_wrap_inline18 pairs, and are needed to further constrain the vertical atmospheric structure of Uranus and Neptune. Improved H tex2html_wrap_inline18 -H tex2html_wrap_inline18 3-0 RV CIA data (intensity and spectral band shape) will be particularly important for that study. The second overtone band of the RV CIA spectra is related with a vibrational single transition ( tex2html_wrap_inline32 ) and double transitions ( tex2html_wrap_inline34 ), where tex2html_wrap_inline36 are the vibrational quantum numbers of two interacting H tex2html_wrap_inline18 molecules (i=1 or 2).

The quantum mechanical methods are employed to compute the spectra of 3-0 RV CIA of H tex2html_wrap_inline18 -H tex2html_wrap_inline18 pairs, with newly developed ab initio induced dipole moments [1] taken into account. Our preliminary results also show good agreement with the existing experimental data. More work is currently underway and we expect the new results to be better than those presented here.

Future model of 3-0 spectra at the temperature range 20-300 K will be distributed freely to all interested planetary scientists.