Computational Spectroscopy

Rotational and vibrational spectroscopies meet theory

To support and guide experiment in the field of rotational, vibro-rotational and vibrational spectroscopies, it is fundamental to have an accurate prediction of their rotational and/or vibrational spectra, and thus of the corresponding spectroscopic parameters. The recording, analysis and interpretation of experimental spectra are often not all straightforward and, more and more frequently, they need the computational support. Computational chemistry and spectroscopy have nowadays reached an accuracy rivaling the experiment. Therefore, they are able to provide a crucial support to the determination of the spectroscopic parameters of interest by means of state-of-the-art approaches.

Computational thermochemistry

Computational thermochemistry is nowadays largely used to determine and/or confirm experimental thermochemical parameters. These range from conformational energies to reaction heats, to dissociation energies, etc... . Its role becomes central when transient species are involved, as radicals, ions and reactive molecules are more difficult to be experimentally studied and as a consequence experimental results are affected by larger errors. To obtain accurate results and quantitative predictions, state-of-the-art computational approaches are employed. These are based on computational composite schemes. It is important to point out that an accurate conformational characterization is the starting point for any spectroscopic study that involves molecular species or complexes characterized by large amplitude motions.

Computational chemistry applied to clusters or isolated molecules

While covalent bonds provide the basic information on molecular structures and energies, non-bonding interactions are responsible of their specific features, thus playing a role in conformational preferences, in molecular recognition mechanisms, in solvation processes, in catalysis and in many other fields. Non-covalent interactions have a common electrostatic nature. They can be non-specific, like van der Waals interactions, or they can involve specific sites of the molecules of interest. In this case, the interactions are the hydrogen, weak hydrogen and halogen bonds, as well as the lone-pair···π interaction. Computational chemistry plays a key role in the understanding of weak interactions and in their correct interpretation.

VMS-ROT Project: Development of Virtual Multifrequency Spectrometer (VMS) for simulation, interpretation and fitting of rotational spectra (ROT)

The Virtual Multifrequency Spectrometer (VMS) is a tool that aims at integrating a wide range of computational and experimental spectroscopic techniques with the final goal of disclosing the  static and dynamic physical-chemical properties "hidden" in molecular spectra. VMS is developed at the Scuola Normale Superiore di Pisa, in the group of prof. Vincenzo Barone. Our research group participated in the development of the Rotational Spectroscopy module.
VMS consists of two parts, namely VMS-Comp, which provides access to the latest developments in computational spectroscopy, and VMS-Draw, providing a powerful graphical interface (GUI) for an intuitive interpretation of the theoretical results which allows direct comparison with the experiment.
In this context, VMS-ROT offers an integrated environment for the analysis of the rotational spectra, with the innovative perspective of an intimate connection to quantum-chemical calculations that can be exploited at different levels of refinement, as an invaluable support and complement for experimental studies