Berlin 2014 – scientific programme
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MO: Fachverband Molekülphysik
MO 20: Electronic Spectroscopy 2
MO 20.3: Talk
Thursday, March 20, 2014, 17:00–17:15, BEBEL SR144
Determination of Excited State Dipole Moments from Electronic Stark Measurements — •Michael Schmitt1, Josefin Wilke1, Martin Wilke1, and W. Leo Meerts2 — 1Heinrich-Heine-Universität Düsseldorf, Insitut für Physikalische Chemie, Düsseldorf, Deutschland — 2Radboud University, Molecular and Biophysics group, Nijmegen, The Netherlands
The dipole moments of electronically excited states may differ considerably from those of the ground state, as a consequence of the altered electron distribution upon excitation. This change of the dipole moment upon electronic excitation has a large influence on solvation dynamics, which is largely governed by the interactions of solute and solvent dipole moments.
We modified the existing setup for rotationally resolved electronic spectroscopy by inserting a pair of Stark plates in the laser-molecular beam interaction region. They consist of a parallel pair of electroformed nickel wire mesh (70 mesh per inch) with a transmission of 95% in the UV. The polarization plane of the incoming laser beam can be rotated by 90∘ inside the vacuum chamber by means of an achromatic λ/2 plate. For the polarization being parallel to the electric field of the Stark plates Δ M = 0 and for the polarization being perpendicular to the electric field Δ M = ±1 selection rules apply.
The spectra of several indole derivatives have been fit automatically using an evolutionary strategy. The nature of the excited states is discussed, using the informations from the excited state dipole moments.