Final Activity Report Summary - QUASAAR (Quantitative spectroscopy for atmospheric and astrophysical research) In order to model our environment, or indeed the many environments that occur in the Universe, one needs to know its molecular constitution. Beyond determining what is there, an essential element to the successful modelling of such an environment is to know precisely how much is there. Molecular spectroscopy allows one to obtain information about molecules by analysing the absorption and emission of light. Since light can travel long distances before being detected and analysed, spectroscopy is ideally suited for remote sensing-one can identify molecules in locations not easily accessible, such as the upper layers of the Earth's atmosphere, interstellar clouds, and the atmospheres of other planets, comets and of cool stars. Not only can one use spectroscopic methods to determine what is there, but also how much is there. The aims of the QUASAAR network were: (1) to provide high-accuracy experimental and theoretical data on molecular transitions needed for measurements in remote environments; and (2) to train early-stage and experienced researchers with the quantitative experimental and theoretical skills to make and interpret such spectroscopic measurements. The multidisciplinary network combined diverse, state-of-the-art experimental techniques with a variety of high-level theoretical methods. To design an experiment capable of carrying out measurements with the accuracy needed for remote sensing, it is necessary to draw on numerous disciplines such as optics, electronics design, vacuum technology, and informatics. Similarly, the theoretical component of the network drew on theoretical chemistry and physics, applied mathematics, and informatics. During the four-year duration of the network, research has been carried out over a broad front. A very large amount of molecular data, relevant for interpreting remote sensing experiments made in connection with atmospheric and astrophysical studies, has been obtained, in particular for molecules of fundamental importance such as water, ammonia, and methane. The new molecular data have found their way into important international databases, most notably HITRAN and GEISA. In addition, new methodology has been developed in both experimental and theoretical areas. Progress has been made with experimental techniques to investigate very highly excited states of molecules, close to the point where the molecule breaks apart. Such states are important for understanding reactions in the atmosphere and in interstellar space. Also, the network has brought together diverse, complementary experimental methods which could be combined to produce molecular data of significantly improved accuracy. Theoretically, new approaches have been developed which allow, at least for small molecules, the first-principles theoretical calculation of molecular spectral data with an accuracy close to that of experiment. That is, theoretical calculations are now a genuine alternative to expensive and difficult experiments. The high-accuracy results of the network research have significant applications in metrology, combustion science and studies of plasmas for industrial purposes. Moreover, highly accurate measurements of molecular energies serve as a unique base tool for molecular dynamics and intra-molecular energy transfer studies. The network fellows have been heavily involved in the network research. Thus, along with the research carried out in the network, a new generation of European researchers has been trained. These researchers are specialised in different aspects of experimental molecular spectroscopy and molecular theory. At the annual network schools, they have been given a broad training in these areas and so they are ready to play a crucial role in planning and interpreting the future European remote-sensing experiments which will be made in connection with atmospheric and astrophysical studies.
