Molecular spectroscopy for atmospheric chemistry and astrophysics

Nicola Tasinato (SNS)
Molecular spectroscopy for atmospheric chemistry and astrophysics

Abstract
Since the earlier experiments in the second half of the 1900, the study of Earth and planetary atmospheres and of the interstellar medium by means of spectroscopic techniques has rapidly grown up. On the one side, remote sensing techniques allow monitoring and accurately retrieving the concentration profiles of atmospheric constituents and trace pollutants, since these molecules have strong rotation and vibration-rotation absorptions in the microwave (MW) and infrared (IR) spectral domains, respectively. On the other side, most of our knowledge about the composition of a variety of astronomical environments has been gained almost entirely thanks to spectroscopic observations: actually, light tells the molecular story thus providing fundamental information on the formation and evolution of stars and galaxies.
In the last years, many efforts have been spent for the development of ground- and space-based observatories (e.g. ALMA, SOFIA, Spitzer, Herschel, Voyager, Cassini-Huygens, ISO, CIRS) which operate from IR to millimeter/sub-millimeter wavelengths and are providing a wealth of spectroscopic information at ever increasing quality in terms of accuracy, spectral coverage, resolution and signal-to-noise ratio. To fully exploit the remote sensing observational data acquired for planetary atmospheres (including that of the Earth) and for the interstellar medium, spectroscopic information needs to be determined for molecules having atmospheric and/or astrochemical relevance. Within this framework, the aim of laboratory spectroscopy is to provide the required spectroscopic knowledge for the species of interest. This represents a huge and time-consuming work that can be accomplished by combining experimental measurements, theoretical modeling and computational simulations.
An overview of the laboratory investigation of the spectroscopic properties relevant for atmospheric and astrochemical applications is given. Attention is devoted to both experimental techniques and theoretical methods showing how the synergism between accurate experiments and state-of-the-art quantum chemical calculations represents the modern approach to unveil the variety of information encoded in molecular spectra. Selected case studies are presented and discussed.