Structure, dynamics and reactivity

Research teams in this area are interested in molecular systems, especially in their structural and dynamical properties under a wide range of environmental conditions. Isolated molecules are analyzed within the theoretical framework of quantum chemistry, along with self-organized mesoscopic structures as complex liquids and solid-liquid mixtures. Several advanced optical techniques allow to characterize spectral and dynamical properties of photo-excited molecular systems, e.g. during relaxation and propagation processes, even in the femtosecond temporal regime. Experiments are conducted not only under standard conditions, but also under high pressure and with very high or very low temperatures.

High pressure chemistry and physics

The research mainly concerns with the study of simple molecular systems under pressure, using the Diamond Anvil Cell (DAC) technique to compress the samples under equilibrium conditions up to 106 bar. These studies are useful to understand fundamental physical and chemical properties of matter and to simulate pressure and temperature conditions occurring in nature, as for example in the Earth interior or in other astrophysical systems. Photochemical effects act at high pressure as a further effective regulatory tool of the reaction mechanism, because the electronic distribution, and thus the molecular geometry, can be modified by a suitable optical excitation. The possibility to appropriately and simultaneously control pressure, temperature and electronic excitation opens new perspectives in solid state chemistry, for example towards a synthesis of materials of technological interest by using only physical methods.

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Ultra-fast spectroscopy

The investigation of the dynamical properties of molecular systems is one of the main research topics at LENS since its establishment in 1991. The research is carried on by means of several optical techniques in which laser pulses as short as a few tens of femtoseconds are used to characterize the spectral and dynamical properties of photo-excited molecular systems. Some examples of research lines are about photochemical and photophysical processes in molecular systems, dynamics of biomolecules and vibrational dynamics of pure liquids and solutions. The research focus is on relaxation processes of electronic excitations of molecules and inter- and intra-molecular electronic energy-transfer processes in order to better understand the behaviour of natural light-harvesting systems. Another field of interest regards different classes of metal complexes which are promising as precursors for the realization of molecular scale devices.

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Molecular spectroscopy

Analysis of isolated molecules in the gas phase offers unique possibilities for a detailed study of their dynamical and equilibrium properties by means of laser spectroscopy methods, without the constrains imposed by the presence of a solvent shell or a crystalline or disordered lattice. Some examples are the ability to follow the evolution of isolated molecules prepared in electronic excited states and to monitor the different reaction channels, to identify the particles produced with photochemical reactions and to determine their quantum state and the kinetic energy released during the process, to drive a photochemical reaction on a specific pathway using appropriate laser pulses. At present also new tools for the identification of materials used in the production and conservation of artistic manufactured articles are under development.

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Soft matter physics

Research on soft matter focuses on the study of a variety of physical systems whose properties are intermediate between liquid and solid states. All these materials, despite their very different nature, share an important common physical feature: soft matter self-organizes into mesoscopic structures that are much larger than the microscopic scale and yet are much smaller than the macroscopic (overall) scale of the material. At LENS we study structure and dynamics of soft matter by means time-resolved laser spectroscopy, exciting the sample impulsively. It is thus possible to follow the sample response over a very wide time scale, from picosecond to millisecond, and investigate a variety of soft matter properties, including molecular vibrations, structural-rotational relaxation, elastic-acoustic propagation and thermal diffusion.

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