Hannover 2013 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 2: Electronic Spectroscopy I
MO 2.2: Vortrag
Montag, 18. März 2013, 11:15–11:30, F 107
[1+1]-REMPI experiments on pyracene — •Melanie Lang, Christof Schon, and Ingo Fischer — Institut für Physikalische und Theoretische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland Süd, D-97074 Würzburg, Germany
Although polycyclic aromatic systems are of great interest for example in optoelectronic applications, the knowledge of electronic structure is still scarce. Here we are interested in pyracene (C14H12, m/z = 180), an alkylated derivative of naphthalene (C10H8, m/z = 128). Pyracene with its two C2H4-bridges represents a more steric hindered aromatic system compared to naphthalene. We investigated the first excited electronic state. Pyracene -a solid substance- was transferred to the gas phase. A [1+1]-REMPI (resonance inhanced multiphoton ionization) process with detection by mass spectrometry was applied. The experiment was carried out with a ns-pulsed dye-laser. We observed a pronounced and intense vibrational structure in the S1 electronic state. Theoretical calculations suprisingly did not determine any significant geometry change upon electronic excitation to S1 whereas S2 gets slightly distorted. Furthermore we suppose vibronic coupling between S1 and S2.