Quantum Dynamics at Novel Types of Conical Intersections

• Applicant: Dr. Foudhil Bouakline
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2016 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 324648380

It is nowadays widely recognized that conical intersections (CIs) are ubiquitous and play a key role in non-adiabatic quantum dynamics of polyatomic molecules. These singularities are characterized by ultrafast radiationless electronic transitions, which are of capital importance in several physico-chemical processes such as vision, photostability of DNA, photosynthesis, and photochemistry of atmospheric and interstellar molecules. Consequently, their study has recently become germane to various research topics in physics, chemistry, and even biology. Until not long ago, most of these studies had focused on standard conical intersections, which occur between two electronic states in the configuration space of internal (vibrational) molecular modes. However, it has recently been demonstrated that CIs can be found in any molecular system having both slow and fast degrees of freedom. Examples of new types of conical intersections include vibrational CIs involving a single electronic state, external CIs in translational laboratory coordinates with ultracold molecules, external CIs based on resonant molecular dipole-dipole interactions, and light-induced CIs occurring even in diatomic molecules. In the present project, we aim to build on the various studies over the last decades on standard CIs and use the accumulated knowledge to investigate quantum dynamics at two novel types of conical intersections: (i) Light-induced conical intersections or glancing intersections created by running laser waves, and (ii) conical intersections between complex-valued electronic potential energy surfaces. These new topologies are only recently introduced, largely unexplored, and expected to play a major role in the control of chemical reactivity. The first and central goal of the project is the derivation of the theory of these novel CIs in the adiabatic picture, thus complementing their only known formalism, given in the diabatic representation. This is important to further understand non-adiabatic phenomena, and disentangle the effects of radiationless electronic transitions and the Berry phase. The theory and models developed in the first stage of the project will then be implemented in numerical codes in order to study the dynamics of molecules interacting with strong laser fields, or with a bath of harmonic oscillators. In practice, we will notably investigate the following, (i) the disentanglement between the Berry phase effect (if any) and non-adiabatic transitions at light-induced conical or glancing intersections, with applications to the stereodynamics of strong-field molecular photodissociation, (ii) the effect of nuclear permutation symmetry on state-selective photochemistry, i.e., on dynamical vibrational or electron localization in centrosymmetric molecules, (iii) the possibility of a combined description of strong laser field simultaneous molecular ionization and dissociation, and (iv) dissipative dynamics in extended molecular systems.

• DFG Programme: Research Grants