Hamburg 2009 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 24: Elektronische Spektroskopie

MO 24.4: Vortrag

Freitag, 6. März 2009, 11:30–11:45, VMP 6 HS-G

Experimental and theoretical investiation of a L_a/L_b conical intersection in tryptamine — •Michael Schmitt¹, Karl Kleinermanns¹, Timothy Zwier², and Michael Nix³ — ¹Heinrich-Heine-Universität Düsseldorf, Institut für Physikalische Chemie — ²Purdue University, Department of chemistry — ³University of Bristol, School of Chemistry

The vibronic spectrum of tryptamine has been studied in a molecular beam up to an energy of 930 cm⁻¹ above the S₀-S₁ electronic origin. Rotationally resolved electronic spectra reveal a rotation of the transition dipole moment direction from ¹L_b to ¹L_a beginning about 400 cm⁻¹ above the L_b origin. In this region, vibronic bands which appear as single bands at low resolution contain rotational structure from more than one vibronic transition. The number of these transitions closely tracks the total vibrational state density in the ¹L_b electronic state as a function of internal energy. Dispersed fluorescence spectra show distinct spectroscopic signatures attributable to the L_b and L_a character of the mixed excited state wave functions. The data set is used to extrapolate to a L_a origin about 400 cm⁻¹ above the L_b origin. DFT/MRCI calculations locate a conical intersection (CI) between these two states at about 900 cm⁻¹ above the L_a origin. The spectroscopic consequences of this CI will be discussed.