9415454 Gamache This project will focus on the development of a theoretical framework to calculate pressure-broadened halfwidths ( ) and pressure-induced line shifts ( ) for atmospherically important species. The halfwidth is the major source of error in remote sensing data and in line-by-line models used to calculate radiative forcing from greenhouse gases. To address these problems, data are needed for thousands of rotational-vibrational transitions. Hence a theoretical model is needed that is computationally efficient and capable of achieving 5% uncertainty in . The resolvent operator formalism of Baranger, Kolb, and Greim (BKG) is the basis of the theoretical approach. Calculations will use realistic molecular dynamics, explicit velocity averaging, and all relevant terms in the interaction potential. Calculations will be done for atmospherically important rotor molecules (H2O, O3, SO2, NO2, H2S) perturbed by N2 or O2 and self-interactions. There are a number of experimental measurements to compare with and test the theory. Once the theoretical questions are resolved, a database of and for atmospherically important transitions will be generated for each species. The vibrational, rotational state, and temperature dependence of the halfwidths and line-shifts will be investigated. The major objective of this work is to improve our confidence in remote sensing results and allow a better determination of the radiative forcing of greenhouse gases.
