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Dipartimento di Fisica - Politecnico di Milano

Ultrafast UV-XUV spectroscopy: towards a complete study of DNA sub-units

DNA absorbs strongly photons in the harmful UV range (200-300 nm), which can potentially induced a photo-damage of the base sequence with serious biological consequences. Nevertheless, the vast majority of excitations do not trigger photoreactions because the excess of energy after UV excitation is efficiently dissipated by DNA on ultrafast time scales. For example, on its fundamental components (nucleobases) these processes take place less than tens of femtoseconds (1 fs = 10-15 s). Therefore, tracking such processes require the development of tools capable of accessing these timescales.



Development of an innovative UV-XUV beamline



We will rely on ideas at the forefront of ultrafast laser science to develop a novel beamline with unprecedented temporal resolution for UV pump – XUV probe studies in gas phase. The work of this thesis will be focused on the generation of ultrashort UV pulses, which will be combined with an existing high-harmonic generation workstation. This unique beamline will allow for the investigation of the photo-physics of DNA subunits in gas phase. This thesis will enable the student to acquire a broad spectrum of competences in vacuum technology, laser development and ultrafast optics.




Ultrafast spectroscopy of biomolecules


This thesis deals with the investigation of the primary steps of the relaxation following photo-ionization of biomolecules (with a special focus on DNA subunits) occurring in a few femtoseconds time scale. In spite of being a problem of fundamental interest of its importance to understand the damage to DNA caused by ionizing radiation, these processes are poorly understood. This is partially explained by the technical challenges to access these ultrafast time scales. Our lab is equipped with a unique monochromator that allows us to select tunable pulses in the 13-60 eV range with 5-fs temporal duration, the shortest ever achieved with this kind of setup. This line will be exploited for the study of the ultrafast photo-ionization dynamics of biomolecules. This thesis will enable you to acquire skills in laser and vacuum technologies, molecular physics and ultrafast spectroscopy.


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