Oberseminar, SS15

Abstract

Abstract

In order to retrieve actual molecular abundances from astrophysical observations of molecular spectral lines, knowledge of the rotational levels excitation schemes is essential. Actual excitation results from a trade-off between photon excitation and collisional excitation by the main constituents of the interstellar gas, molecular hydrogen, and, to a lesser extent, atomic hydrogen and helium. These inelastic collisional rates are almost always obtained from theoretical investigations, by computing classical or quantum dynamics of the interaction of molecules with these colliders. In order to assess the quality of the computations, a systematic comparison with experiments is being undertaken. Observables are mainly integral or differential cross-sections as well as pressure broadening cross sections. We shall present recent computations and various types of experiments, in order to illustrate the need for both laboratory work and computational work for the quantitative understanding of astrochemistry.

Abstract

Abstract

New insights into atmospheric ion processes and their implications are discussed. These processes include interactions between ions, free electrons, trace gases, and aerosol particles. Emphasis is placed upon ion-induced aerosol formation. Another fascinating aspect of atmospheric ions is their role as a tool for obtaining unique information on important atmospheric trace species, including trace gases and aerosol particles. This application yields information also on atmospheric trace species having key roles in the atmospheric climate system and in atmospheric environmental problems.