The Abundances of Methane and Ortho/Para Hydrogen in Uranus and Neptune: Implications of New Laboratory 4-0 H(sub 2) Quadrapole Line Parameters

摘要

The tropospheric methane molar fraction (f(sub ch4,t)) and the ortho/para hydrogen ratio are derived for Uranus and Neptune based on new determinations of spectroscopic parameters for key hydrogen features as reported by Ferguson et al. (1993, J. Mol. Spec 160, 315-325). For each planet, the relatively weak laboratory linestrengths (approximately 30 and 15 less than the theoretical 4-0 S(0) and S(1) linestrengths, respectively) results, when compared to analyses adopting theoretical values, in a 30 decrease in the tropospheric methane ratio and a comparable increase in the pressure level of the optically-thick cloudtop marking the bottom of the visible atmosphere (P(sub cld)).