Dynamical processes in ultralong-range Rydberg molecules

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Ultralong-range Rydberg molecules (ULRM) represent an exoticmolecular species with a novel chemical binding mechanism. Theyhave been predicted theoretically in 2000 by Greene, Sadeghpourand Dickinson and were firstly found experimentally in 2008 by Pfauet al employing photoassociation spectroscopy. Since then ULRMhave become an independent research area closely interacting withquantum optics, quantum many-body physics and ultracold atomicphysics. Consisting of a disparate bound state mixture of Rydbergand ground state atoms ULRM exhibit huge bond lengths and dipolemoments and inherit the sensitivity to external fields. Whileinvestigations on the structure of diatomic and polyatomic ULRM havebeen demonstrating the enormously rich phenomenology and thepossibility to design bound molecular quantum states via fields, verylittle is known about quantum dynamical processes, or, in other words,Rydberg ULRM chemistry. This proposal aims at closing this gap bydeveloping a systematic approach to the underlying elastic andinelastic processes taking place for ULRM. It will, as such, provide amajor leap forward with respect to the characterization of these novelmolecular species and their Rydberg chemical reaction dynamics.Specifically we will explore the wave packet dynamics on single andmultiple adiabatic potential energy surfaces which we obtain fromextensive electronic structure calculations of ULRM. Pump-probetechniques will be employed and emulated to prepare and probe theinitial and final time wave packet. On a single surface the quantumdynamics is adiabatic electronic character and we are interested inthe multiple interference and scattering events possibly dispersing,delocalizing and fragmenting the original vibrational wave packet. Inthe case of several potential energy surfaces which interact locally incoordinate space we will probe the possibility of ultrafast nonradiativedecay processes through either avoided crossings or conicalintersections. Spin interaction effects due to the spin of the Rydbergelectron and the electronic and nuclear spin of the ground stateatoms, as well as spin-orbit interaction effects for both the Rydberg electron and the interaction with the ground state atoms shall beincluded. A variety of different elastic and inelastic Rydberg chemicalprocesses will be investigated, including spin changing collisions,associative ionization and heavy Rydberg state formation as well as inparticular recombination and dissociation processes. External fieldswill be used to control the geometry of the molecules and to steer thecorresponding dynamics. The employed wave packet Propagation methods will be based on multi-dimensional grids in position spacevia discrete variable representations and the Multi-ConfigurationTime-Dependent Hartree approach for multi-mode vibrationaldynamics of molecules.