Hannover 2010 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 5: Femtosecond Spectroscopy I
MO 5.7: Vortrag
Dienstag, 9. März 2010, 15:30–15:45, F 102
CRASY: Correlated Rotational Alignment Spectroscopy Resolves Isotopic Structure — •Christian Schröter, Kyriaki Kosma, 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. Due to the inherent low resolution of femtosecond experiments, this spectroscopy cannot resolve the details of isomeric and isotopic structure. This is a problem, because molecular properties are intrinsically tied to the molecular structure. Here we present CRASY-experiments which simultaneously resolve structural and electronic properties of molecular compounds.
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. They can be extracted by Fourier-transformation. Since every mass-channel supplies its own rotational spectrum mass-CRASY allows to extract rotational frequencies for single isotopes and isomers.
The mass-CRASY method was tested in experiments with CS2. Rotational frequencies of rare isotopes can be extracted without synthesizing expensive enriched isotopic mixtures. Results are presented.