Coherent electronic and nuclear flux densities during adiabatic unimolecular processes in diatomic molecules

• Applicants: Professor Dr. Jörn Manz; Dr. Jhon Fredy Pérez Torres
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258798244

Intuition suggests that electrons and nuclei should flow together during electronically adiabatic unimolecular processes such as chemical reactions, vbrations or dissociations in the electronic ground state. Experimental advances in femto- and attosecond chemistry call for quantum dynamical simulations of coherent electronic and nuclear flux densities (CENFD). No lasting progress had been made in this field, however, since the discovery of the Schrödinger equation in 1926, until very recently. The main obstacle has been the Born-Oppenheimer approximation (BOA), irrespective of the fact that the BOA is applied quite successfully in quantum chemistry and other domains of quantum reaction dynamics. Recently we, together with Prof. Dr. Dennis J. Diestler, a guest professor from the USA and Prof. Beate Paulus (FU Berlin), achieved a breakthrough in this field, by calculating the CENFD for the simplest system, namely aligned H2+ in the electronic ground state (i.e., the prototype) undergoing vibration. The results were obtained by two independent methods: a ¿spectral method¿, in which the wave function is expressed as a linear combination of vibronic eigenfunctions of the complete Hamiltonian; the ``scaled coupled channels" method, developed in cooperation with Prof. Diestler, which utilizes only the BOA wave function as ¿input¿ to a hierarchical procedure. The spectral method provides accurate CENFDs, which serve as references for assessing the quality of scaled coupled-channels results. The two are in excellent agreement for the prototype. The aim of the work proposed here is to extend this promising approach to more demanding processes and to more complex aligned or isotropic distributions of diatomic systems with two or more electrons. These include the following: vibrational revivals, dissociation, and competition between vibration and dissociation, in the prototype, in asymmetric one-electron systems, such as HD+, and in symmetric and asymmetric systems with a single valence electron (e.g., Na2+ and LiH+); analogous processes in two-electron systems, such as H2, the two-electron prototype, or in systems with two or more active valence electrons, such as Na2 and LiH, and F2. These examples will show, for the first time, the influence of electron-electron repulsion on the CENFDs.

• DFG Programme: Research Grants