Ricerc@Sapienza

Raman spectroscopy is currently employed as one of the most powerful tools for the investigation of the nature of matter. It employs a focused laser beam that selects a specific portion of the sample (when used in conjunction with a microscope, the selected area can be as small as 1 micron squared). The light reflected and scattered by the sample is analyzed by a spectrometer, and the few photons (light waves) that have changed their energy (frequency) during interaction with the sample are identified in the so-called Raman spectrum. Peaks in the Raman spectrum reveal specific molecules, or details of the bandstructure of solids, or the conformation of proteins. Raman spectroscopy is already well represented at Sapienza. Here we propose to extend the pre-existing instrument selection by coupling to a Raman spectrometer employing an infrared laser (wavelength of 1064 nm) a purposely designed microscope now commercially available.
Raman spectroscopy has recently played a key role in the study of graphene. Therein the resonant nature of the interaction between the excitation laser light and the electrons modifies the frequency and the lineshape of the Raman peaks. The use of infrared lasers instead of visible lasers enables the Raman investigation of a new range of electron energies and of new portions of the unique band structure of graphene, much closer to the Dirac point, whose discovery lead to the Nobel Prize in Physics in 2010.
Raman spectroscopy is a purely photonic technique hence contact-less, ideal for investigating artworks and biosystems, however, the focused visible laser light can induce a strong temperature increase or even permanent damage in the sample. Infrared light is much less strongly absorbed than visible light by e.g. cellulose and pigments, or by proteins and fluorescent chromophores. An infrared Raman spectrometer would permit Raman studies of precious artworks and of light-sensitive biosystems with strong levels of natural fluorescence.