Mainz 2017 – scientific programme

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MO: Fachverband Molekülphysik

MO 15: Environment Controlled Processes

MO 15.3: Talk

Thursday, March 9, 2017, 15:15–15:30, N 6

Femtosecond spectroscopy of the solvated electron in liquid ammonia over a wide range of excitation energies — •Tim Vogler, Jörg Lindner, and Peter Vöhringer — Institut für Physikalische und Theoretische Chemie, Universität Bonn

We recently reported on the vertical and below-band-gap ionization of liquid-to-supercritical ammonia employing photolytical excitation energies E_g of 9.3 eV [1] and 6.2 eV [2], respectively. In these studies the so called escape probability, i.e. the fraction of solvated electrons that are able to escape from their parent molecule, was around 70% in the first case and only 5% in the latter one (at room temperature and a pressure of 300 bar). This dramatic change in dependence on E_g opens up a very attractive window for further investigations: While the previous work puts special emphasis on the quantification of the escape probability under varying thermodynamic conditions, we now determined its behavior as a function of the excitation energy E_g.

To do so we extended our femtosecond pump-probe-spectrometer with a tunable UV light source providing a wide and gapless range of excitation energies E_g from 6 eV to 12 eV, implying a two-photon dependence of the ionization mechanism as found in [1]. Finally, the experimental results can be interpreted with a model regarding the optical band gap of liquid ammonia, which is around 8.2 eV [2].

[1] J. Urbanek et al., J. Phys. Chem. B 116.7 (2012),

[2] J. Urbanek and P. Vöhringer, J. Phys. Chem. B 118.1 (2013)