Knowledge Bank

Far wing absorption is important in determining long path atmospheric absorption between strong adsorption bands. Development of a detailed dynamical theory of wing lineshapes for atmospheric molecules is a challenging task. A fully quantum mechanical, time dependent, perturbative $theory1$ has been used to evaluate far wing absorption for the 404-515 self-broadened H2O rotational line. The predicted absorption coefficient increases with temperature, in contrast to experimental observations of a strong negative temperature dependence. Replacement of an Anderson-like ad hoc cutoff by a formal resummation of the perturbation series yielded no improvement. We conclude that perturbative methods using multipole expansions are not adequate for this system. Preliminary calculations for an Ar-HC1 test case using a non-perturbative technique, the Recursive Residue Generation Method,2 will be presented.