Institut des Sciences Moléculaires d'Orsay




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Accueil > Séminaires > Année 2012 > Séminaire Maria Novella Piancastelli (15 mai 2012)

Séminaire Maria Novella Piancastelli (15 mai 2012)

Laboratoire de Chimie Physique-Matière et Rayonnement, Université Pierre et Marie Curie UMR 7614

Time-resolved studies of molecular core-excitation dynamics

Molecular core excitation or ionization produces an intermediate state with a
deep electron vacancy, which subsequently decays on a short time scale. The typical
decay patterns for molecules consisting of light atoms involve Auger electron
emission, leading to final states with valence holes. Such processes can be
accompanied by a wealth of molecular dynamics, including nuclear motion or
fragmentation. Depending on the depth of the core hole, typical decay times range
from few femtoseconds to hundreds of attoseconds.

Studies of core excitation-decay processes are usually performed with tunable
sources such as synchrotron radiation facilities. However, the time structure of such
sources does not allow the access to the femtosecond-attosecond time scale.

I will discuss two methods to investigate complex decay dynamics on such a
short time span, and provide some examples for each.

The first possibility is to use the so-called “core-hole clock”, meaning the
possibility of using the core-hole lifetime as upper limit and of observing phenomena
such as ultrafast dissociation taking place during the electron decay.

The second possibility is related to a new generation of tunable sources, namely
the free-electron lasers. At some of the new facilities, the light can be provided very
short pulses, down to a few femtoseconds, allowing the observation of phenomena
such as sequential double-core-hole formation.

Affiche M. Novella Piancastelli 2012 - 164.1 ko