Dresden 2011 – scientific programme

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MO: Fachverband Molekülphysik

MO 12: Femtosecond Spectroscopy III

MO 12.7: Talk

Wednesday, March 16, 2011, 12:00–12:15, TOE 317

CRASY: Correlated Rotational Alignment Spectroscopy Resolves Cluster Fragmentation — •Christian Schröter, Ingolf-Volker Hertel, and Thomas Schultz — Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin

Femtosecond-pump-probe-spectroscopy is a common tool for the investigation of structure and dynamics of electronic states in atoms, molecules and clusters. A problem with non-covalently bound clusters is the easy fragmentation either in the excited or the ionic state. As a result the spectroscopic data can*t be assigned to a specific cluster size.

CRASY is a method which combines rotational spectroscopy in the time domain with femtosecond-pump-probe experiments. An IR pulse generates a coherent rotational wave packet by means of non-adiabatic alignment. After a variable delay, we probe the wave packet by a UV pulse which excites and ionizes the molecule via a resonant electronic state. If we detect ion-masses (mass-CRASY), the ion signal is modulated by the rotational frequencies encoded in the rotational wave packet and can be extracted by a Fourier-transform. By correlating the ground state molecular structure with the ion signals, we can resolve fragmentation pathways and assign size selected cluster data.

The CRASY method was applied to the non-linear molecule Butadiene. We observe fragmentation of non-covalent and covalent bonds in the butadiene-molecule and its clusters. With the ability to characterize ground state structure which gave rise to a mass or electron signal, mass-CRASY resolves the spectroscopic problem described above.