270144 VO Quantum Dynamics of Molecular Excitations (2017W)

Inhalt und Methode
This Lecture is intended to provide a state-of-the-art survey on non-trivial, dynamic quantum signatures in molecular excitations and their impact on the fundamental amplitudes of elementary physical & chemical change, on ultrashort time-scales. In the so-called semi-classical regime of fundamental light-molecule interaction, the optical perturbation field launching the excitation dipole is classical , whereas quantum mechanics should apply to molecules regardless of size (vide infra) provided the internal molecular states/modes are few and discrete, and external correlations from the environment are neglectable. In this limit, the key theoretical entry is the concept of the coherent Wave Packet (WP, E. Schrödinger 1926). According to this gedanken-experiment, a superposition of vibrational eigenfunctions (WP), initially localized, e.g. in parabolic space of di-atomics ,with a (Gaussian) probability distribution spreads over positional coordinates in the course of its back-&-forth inter-atomic round-trips, but changes its motional behavior by undergoing self-interference, amplitude splitting and generating fractional quarter-to -half revivals at intermediate times. In this situation, the colliding pair announces the quantum-mechanical motional domain with an ongoing tendency to finally reaching the full revival domain by restoring the initial phase of the vertical FC-excitation state, at long times.
Ziele
The Lecture is structured to communicate quantum-dynamic phenomena, from scratch, starting from di-atomics to intermediate-size and large-sized molecules, covering vibronic-exciton coupling and ending up with transfer of electronic energy and/or charge transfer in molecular aggregates and biological light harvesting systems. The talks will expose how to think about elements of molecular quantum coherence in vibronic energy transfer and electron transfer reactions and will particularly study roles played by intramolecular vibrations and their couplings to electronic dipole transitions using quantum - wavepacket spectroscopies. As a net effect, one learns about the mechanistic role of vibrations and perceives the early stage of chemical change (chemistry!) at the microscopic molecular level. At the core of solar photochemistry subsequent to molecular excitation, the use of light is to propel electrons and chemistry is about coercing electrons to move via electron-vibration coupling thus storing the energy of light in a form that can be captured in molecular configurations or bonds.
The pedagogical aim of this Lecture is to moderate the exacting concept of molecular quantum excitations in terms of useful surrogate pictures, schemes and models, in a first approach, minimizing the mathematical efforts, substantially. Once this level can be perceived, a more advanced access under the umbrella of theoretical descriptions will explain the particulars & details in an endeavor to quantify measurements, data and observables in accordance to state-of- the art concepts in the lingua franca of text-book quantum dynamics. In toto, the Lecture may provide motivation for advancing the frontiers in this era and their interdisciplinary context in the fields of physics, chemical physics and biophysics, with special priorities placed on the hot topics in organic electronics, molecular and quantum dot photo-voltaics, synthetic light-to-energy transformers, biomimeting artificial light harvesters etc.