Mathematics – Logic
Scientific paper
Oct 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998phdt.........7f&link_type=abstract
Thesis (PHD). MICHIGAN TECHNOLOGICAL UNIVERSITY , Source DAI-B 59/04, p. 1715, Oct 1998, 146 pages.
Mathematics
Logic
Collision Induced Absorption, Stellar Atmospheres, Neptune, Uranus
Scientific paper
The collision induced absorption (CIA, hereafter) spectra of H2-H2 are known to play an important role for modeling of both zero- and low-metallicity, cool dense stellar atmospheres and H2 rich planetary atmospheres. The computations of rototranslational (RT, hereafter) and the three lowest rotovibrational (RV, hereafter) CIA spectra of H2-H2 pairs are presented in the frequency range from the far-infrared up to near-infrared, at temperatures ranging from 1,000 to 7,000 K for the first time based on the first principles (Fu et al., 1998). The two essential inputs for the computations are the newly developed ab initio collision-induced H2-H2 dipole functions (C. Zheng. Ph.D. Dissertation) and the carefully chosen isotropic H2-H2 potential (Ross et al. 1983), both of which are suitable for high temperatures. We have computed the CIA coefficients of the vibrational transitions with υ1, υ υ1' and υ2' ≤ 3 rigorously, and have estimated CIA coefficients of single vibrational transitions with υi < 3,υi' > 3 in the first, and the second overtone bands. The dependence upon rotational states of H2 has been taken into account. One of important application of these spectra at high temperatures is the modeling of stellar atmospheres of cool carbon and oxygen rich stars with various metallicities, gravities and effective temperatures. We present a numerical method (Borysow et al. 1998) to compute the collision induced rotovibrational absorption spectra of H2-H2 complex in the second overtone band of hydrogen in the frequency range ~0.86-0.77μm. at temperatures from 20 to 500 K. Model spectra closely reproduce the latest quantum mechanical results (Fu et al. 1998) which are found to agree with experimental CIA spectra typically within 20-30%. This simple analytical model will be applied to study atmospheric structures of the outer planets, especially those of Neptune and Uranus, in the near-infrared and close to visible regions of the spectrum. Calculations of the far wings of Raman rotational spectrum of N2 have been performed and compared with existing measurements. The wings of both the allowed and the collision induced spectra, have been taken into account. We demonstrated that the contribution of the allowed spectrum dominates the spectral intensity in the far wings, instead of the contribution of collision induced light scattering (CILS, hereafter) spectrum as believed before (Bancewicz et al. 1992.)
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