Who: A. Trabattoni (Dep. of Physics, Politecnico di Milano, Italy)
Place: Donostia International Physics Center (DIPC). Paseo Manuel de Lardizabal, 4, Donostia
Date: Wednesday, 25 February 2015, 12:00
Attosecond electron dynamics in complex molecular systems
Department of Physics, Politecnico di Milano, Milano, Italy.
The investigation of ultrafast electron dynamics in matter is of crucial importance in the understanding of many biological phenomena, such as cellular respiration, catalysis and photosynthesis. In particular, the application of attosecond pulses to complex molecular systems offers the possibility to initiate and observe ultrafast charge transfer along molecular skeleton, that is expected to occur on a temporal scale between hundreds of attoseconds up to few femtoseconds, preceding any nuclear rearrangement .
In the seminar the speaker will present the theoretical and experimental tools that are on the basis of attosecond molecular science, then he will turn to the description of some important results obtained in the ELYCHE high-energy attosecond laboratory ? Department of Physics, Politecnico di Milano.
First the investigation of ultrafast dissociative dynamics of N2+ induced by XUV attosecond pulses will be presented, demonstrating the possibility to follow and control the ultrafast relaxation dynamics of the excited electronic states of the molecular cation activated by the XUV light, which is clearly of high interest for the complete understanding of photo-stability of molecules exposed to ultraviolet radiation, for example in the photochemistry of the Earth?s upper atmosphere .
Then the speaker will concentrate on the first experimental demonstration of charge migration in a biologically relevant molecule, the amino acid phenylalanine, by using attosecond pulses. The phenylalanine molecules were photoionized by sub-300-as isolated attosecond pulses and subsequently probed by 4-fs waveform-controlled visible/near infrared probe pulses. The parent ion and the molecular fragments were collected in a mass spectrometer, and the time-dependent mass spectrum was investigated as a function of the pump-probe delay.
The result of the experiment, together with standard time-dependent density-matrix simulations, clearly demonstrates the production of a purely electronic dynamics along the molecular ion, characterized by an ultrafast oscillation of the hole density, with a period that is shorter than the vibrational response of the molecule .
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 F. Calegari et al, Science 346, 336-339 (2014).
(host: G. Benedek)