SAMOP 2023 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 15: Rotational- and Vibrational-resolution Spectroscopy

MO 15.1: Hauptvortrag

Donnerstag, 9. März 2023, 11:00–11:30, F142

Excited state dipole moments from rotationally resolved Stark spectroscopy — •Michael Schmitt, Matthias Zajonz, and Marie-Luise Hebestreit — Heinrich-Heine-Universität Düsseldorf, Institut für Physikalische Chemie I, Universitätsstraße 26.43.02

Rotationally resolved electronic Stark spectroscopy is a versatile tool for the accurate determination of rotational constants of molecules in both electronic states, connected by the electronic transition, centrifugal distortion constants, barriers to hindered internal motions, transition dipole moments, and the permanent dipole moments of both states. The latter provide an easy access to the electronic nature of the excited state, because they differ in size and in direction for different electronic states. The most reliable values for dipole moments of ground and electronically excited states are obtained from gas phase electronic Stark experiments, since the dependence of the frequency shift of individual rovibronic lines from the electric field strength yields immediately the dipole moment in ground and excited state. A variation of the solvatochromic effect will be presented, namely the thermochromic effect, which is able to yield dipole moment changes upon electronic excitation of molecules in solution that are largely independent of the solvent used, to close the gap between gas phase dipole moment changes and those obtained in solutions. Although used for many years in organic chemistry, the Lippert-Mataga theory has severe deficiencies, which will be highlighted in the contribution. We will present a thorough analysis of the photo-physics of the six different positional isomers of cyanoindole in the gas phase and in solution.