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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 107: Emerging Topics in Chemical and Polymer Physics, New Instruments and Methods

CPP 107.8: Vortrag

Freitag, 20. März 2020, 11:45–12:00, ZEU 255

Quantum tunnelling in the Marcus inverted regime — •Eric R. Heller and Jeremy O. Richardson — ETH Zürich, 8093 Zürich, Switzerland

Electron transfer rates between weakly coupled states are predominantly calculated using Marcus theory. Due to its inherent classical character, however, experimental reaction rates can deviate from the Marcus result by several orders of magnitude due to the influence of quantum tunnelling and zero-point energy. These effects prove to be of particular importance in the so called ``inverted'' regime, where reaction rates become smaller with increasing thermodynamic driving force.

In principle the correct quantum mechanical rate can be obtained by applying Fermi's golden rule. This, in turn, requires knowledge of the nuclear wavefunctions of the two reactive wells, which are not accessible for all but very small systems.

Semiclassical instanton theory is able to capture nuclear quantum effects in a numerically efficient way allowing application to complex, anharmonic systems. Recently this method has been extended to describe the inverted regime by locating an optimal tunnelling pathway formed by two trajectories, one of which travels in negative imaginary time giving a picture reminiscent of the scattering of particles and antiparticles.

The method thus constitutes a semiclassical path-integral version of Fermi's golden rule applicable not only to electron-transfer reactions but also light-matter interactions, electrochemistry and many more.