ELFT HÍRADÓ

[Szeminárium koordinátor <sem-admin AT szfki.hu>]

SZFI SeminarSándor PéterWigner RCP SZFIMolecular Strong-Field Ionization 
viewed with Photoelectron Velocity Map ImagingTuesday, 27 October 2020, 
10:00, video conference, https://letsmeet.wigner.hu/szeminariumStrong-field 
ionization is the key first step of the 3-step model which explains phenomena 
such as high-harmonic generation and attosecond pulse generation, which are 
currently at the forefront of ultrafast science. By understanding the changes 
that ionization brings about in the atomic/molecular system, one hopes to 
make the latter two processes more efficient. In my talk I will highlight 
experiments of molecular strong-field ionization that show that in contrast 
to earlier assumptions, even at the lowest intensities required for 
multi-photon ionization, not just the lowest energy, but higher-lying ionic 
states are also populated. For halogenated methane molecules (systems that 
can be regarded as essentially triatomic), different ionization-dissociation 
pathways are identified with the help of a coincidence Velocity Map Imaging 
apparatus that maps photoelectrons according to their vector momentum in 
coincidence with the accompanying ion. Furthermore, we follow nonadiabatic 
temporal dynamics of the electronic structure of the ion on a few tens of 
femtoseconds scale with using ultrashort pulses of ~9 fs in duration and 
interpret the results with ab-initio electronic structure calculations. We 
find that the dynamics on the neutral and ionic state potentials are not 
solely driven by the color content of the exciting laser pulses, but instead 
it is really their shortness in time—relative to nuclear motion—that 
determines the outcome of the experiment. This result has the implication 
that one can indeed 'freeze' the effects of molecular vibrations on 
photoionization if the interaction time is kept sufficiently 
short. Minden érdeklődőt szívesen látunk! - Everyone is welcome to 
attend.Róbert Juhászsem-admin AT szfki.hu