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Rotational Spectroscopy

Rotational spectroscopy of ions, radicals, molecules and isotopologues of astrochemical/astrophysical interest

Our knowledge of the universe chemical inventory has been obtained and continuously updated by means of astronomical observations, which have revealed a plethora of molecular species, thus demonstrating the rich chemistry of the universe. The observation of gas-phase species is usually performed using rotational spectroscopy, which can be undertaken from the ground. This requires previous measurements to be carried out in the laboratory. This new branch of chemistry, also involving both physics and astronomy, is related to the observation of molecules, the detection of their spectroscopic features providing the unequivocal proof of their presence in space. One of the major aims of astrochemistry is also to understand how these molecules are produces in space, with particular interest on the formation of aminoacids, nucleobases, and prebiotic species in general. The latter represent nowadays one of the main targets of astronomical detections.

Spectroscopic characterisation of biomolecules building-blocks and clusters of atmospherical, chemical and biological interest

The interactions between molecules and surrounding environment, like solvents or ligands, constitute the basis of the structure-activity relation, and thus need to be accurately described. To gain a correct description of biomolecules, it is necessary to scale down the system, looking for characteristic building-blocks that are representative of the biological proprieties and activity. A good description of these key-units is acheivable by the supersonic expansion spectroscopy, which allows the investigation of the behavior of these species in high-vacuum and without matrix or solvatation effects. Furthermore, this technique allows also the accurate characterization of the non-covalent interactions occuring.

Molecular structures and force fields from rotational and ro-vibrational spectra

The analysis of rotational spectra allows to determine spectroscopic constants for different isotopic species, from which very accurate molecular structures can be calculated . Valuable information on molecular force fields can also be obtained from rotational spectra in excited vibrational states.

Lineshape analysis of spectra of atmospheric species

Minor components of the atmosphere, such as ozone, nitrogen and sulphur compounds, halogenated hydrocarbons etc., may produce important enviromental effects. These species can be monitored using remote sensing methods based on spectroscopic techniques.  Accurate laboratory data on pressure broadening coefficients of rotational lines are essential to retrieve quantitative information from the atmospheric spectra.

Sub-Doppler spectroscopy by the Lamb-dip technique

The Lamb-dip technique improves the resolution power by a factor of ten, so that hyperfine structures of rotational lines can be more easily detected. In this way weak electric and magnetic interactions between molecular rotation and nuclear spins can be revealed.