QUCUMBER · Quantum Control of Ultracold Molecules By Electric Fields

The study of molecular collisions at the lowest possible energy has emerged as an exciting research frontier. At low energies the wave-character of matter leads to exotic scattering phenomena that reveal the fundamental mechanisms of molecular collisions. Crossed beam methods are ideal to probe collisions with the highest detail, but the lowest energy currently achievable is not sufficient to fully harvest these possibilities. Building upon my recent breakthrough in state-to-state merged beam scattering at record-low energies, the aim of this project is to reduce the currently attainable collision energy by another 2-3 orders of magnitude by combining Stark deceleration, merged beams, laser cooling and velocity map imaging. Using two distinct systems that are characteristic for a large class of molecular interactions, I will measure hitherto unexplored quantum features in the state-to-state integral and differential cross sections. For atom-molecule systems, I will measure scattering resonances and image how the resonance region dominated by a few partial waves evolves into the pure quantum regime where only a single partial wave remains. For collisions between dipolar molecules, I will experimentally study a peculiar self-polarizing effect, probing fundamental features of the long-range dipole-dipole interaction that can be steered from attractive to repulsive. For both systems, I will manipulate the cross sections using external electric fields, and study how the partial waves transform during the collision. The proposed research program will directly visualize how molecular collisions transform from hot into ultracold at the full quantum mechanical level, providing excellent tests for quantum theories of molecular interactions. It will bridge the gap between the ultracold quantum physics and physical chemistry communities, and will lay the foundations for a new era in the rich history of elucidating molecular reaction dynamics using crossed molecular beams.