Demos.MolElectronic.Main

WavePacket demo examples: Electronic excitation of small molecules

The electronic degrees of freedom can be directly excited by interaction of an external electric field, E(t), with the transition dipole moments, μ(R), of the molecule under consideration. For most cases, this interaction can be treated within the framework of the semi-classical approximation, H_int=H−E(t)·μ(R) which couples the vibrational dynamics, e.g., on gound and excited state surfaces.

In modern femtochemistry work, electronic excitation is achieved by means of ultrashort laser pulses, sometimes with especially designed pulse shapes. Apart from high excitation probabilities, the goal is to reach a high state selectivity.

Electronic excitation of the OH radical

A frequently chosen example for the state selective, electronic excitation of molecules is the OH radical ("one-dimensional model of water"). Emphasis is on the vibrationally state selective transfer of population between ground and excited electronic state. Learn more ...

Electronic excitation of the HCl cation

For the example of HCl cation, the effect of extremely short and intense pulses on a (sub-)femtosecond timescale is studied. Emphasis is on the validity of the (Floquet) picture of photon dressed states in the limit of pulses encompassing fewer and fewer optical cycles. Learn more ...

Isomerization of the retinal molecule

The photoinduced isomerization of the retinal molecule in rhodopsin is considered as the primary step in vision. Here it serves as a real-life example for the importance of avoided crossings and conical intersections in photochemical and photobiological processes. Learn more ...

Internal conversion of the pyrazine molecule

The ultrafast internal conversion from the S₂ to the S₁ electronic state of the pyrazine molecule (C₄N₂H₄) proceeds via a low-lying conical intersection of the respective potential energy hypersurfaces. Note that this intersection is not(!) due to a Jahn-Teller effect but is only partially symmetry induced! In the 1990s years, the vibronic dynamics of this system has become a quasi-benchmark system for various numerical techniques to treat intramolecular non-adiabatic quantum dynamics. Learn more ...