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Title: Ultrafast dynamics in gas-phase building blocks of life
Author: De Camillis, Simone
ISNI:       0000 0004 6425 2573
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2017
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Ultrafast electron dynamics are responsible for the physical and chemical properties of molecular systems. They can induce variations in the local reactivity as well as in the nuclear arrangement, both of which ultimately determine the making and breaking of molecular bonds. This thesis presents pump-probe measurements of femtosecond and attosecond electron dynamics in biomolecular building blocks of DNA and proteins, namely nucleosides and aromatic amino acids, characterised by a large degree of stability due to their efficiency in converting electronic energy into vibrational energy within picosecond and sub-picosecond timescales. Low intensities of UV laser radiation are sufficient to access the electron wave-packet evolution from the first excited state of the analyte along the corresponding potential energy surfaces. In a bottom-up approach to investigate the photo-physical properties of DNA and peptide systems, de-excitation dynamics of larger building blocks, have been studied. The bonding of the sugar ring to the nuclebases, as well as of the glycine moiety to the aromatic chromophores, was observed to speed up the relaxation process. These results are discussed in terms of alternative non-radiative deactivation channels opened up by the added units. Much faster dynamics can be initiated by attosecond XUV irradiation, where the superposition of many electronic states produces pure electron motion preceding any nuclear rearrangement. Cutting-edge laser technology has made possible the observation of ultrafast charge migration in tryptophan by looking at the doubly charged immonium ion channel. The signal modulation with period of 4 fs corresponds to the electron beating between the amino group and the side-chain indole. These results represent the first ever time-resolved measurements of coherent electron motion in complex biomolecules, which pave the way for steering electron dynamics and controlling molecular reactivity.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available