Heidelberg 2015 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 22: Femtosecond Spectroscopy 3
MO 22.6: Vortrag
Freitag, 27. März 2015, 12:15–12:30, PH/HS1
Ultrafast Dissociation Dynamics of Superexcited Nitrogen — •Johan Hummert1, Martin Eckstein1, Daniel Strasser2, Marc J. J. Vrakking1, and Oleg Kornilov1 — 1Max Born Institut, Berlin, Germany — 2Institute of Chemistry, The Hebrew University of Jerusalem, Israel
Understanding relaxation pathways of neutral superexcited states in elementary molecules is important to model the chemistry of environments exposed to XUV and other ionizing radiation. Such species occur in terrestial and extraterrestrial atmospheres and in man-made environments. Additionally the coupling of electronic and nuclear degrees of freedom in superexcited states is particularly interesting since the Born-Oppenheimer approximation is often strongly violated.
In this experimental work we investigate dissociation dynamics of superexicted states of molecular nitrogen excited by pulsed XUV light. We employ a high harmonic generation source in combination with a time-compensating XUV monochromator to select the 15th harmonic of a 790 nm IR laser pulse at 23.6 eV, which is just below the threshold for dissociative ionization of N2 (24.25 eV). A second laser pulse at the wavelength of 790 nm probes the highly excited molecules or fragments after a time-delay ionizing them to produce the detected N+ ions.
The recorded transient signals demonstrate both a very quickly decaying component (about 40 fs) as well as a long-lived contribution. Preliminary assignments suggest competition between predissociation from Rydberg-type states converging to the ionic C2Σu+ state and autoionization leading to bound ions.