Stereodynamic Control of Cold Molecular Collisions

University Of Nevada Las Vegas, Las Vegas NV

Investigators

Abstract

Chemists have long sought to control the outcome of chemical reactions. This control requires a molecular level understanding of the underlying mechanisms and reaction pathways. One approach to control the outcome of chemical reactions and molecular collisions is through stereodynamics, i.e., controlling their relative orientations and alignments as they approach each other. This control is even more effective at temperatures close to a kelvin and below where quantum effects become significant due to the wave behavior of matter. Such control of molecular interactions is paramount to emerging quantum technologies such as quantum information processing and quantum computing that use cold and ultracold molecules in controlled environments and whose interactions are manipulated by external fields. The proposed research explores how molecular interactions can be controlled through stereodynamics and how such control can be extended to chemical reactions, thus benefitting emerging quantum technologies that use cold trapped molecules. This work transcends disciplinary boundaries and the computational algorithms developed as part of this research are applicable to molecular processes in diverse areas of chemistry, physics, and astrophysics. Cold and ultracold molecules are rapidly emerging as new paradigm for controlled studies of molecular collisions and chemical reactions. The ability to create them in selected motional, internal and orientational quantum states allows “chemistry-on-demand” experiments in the deep quantum regime where the reaction outcomes are strongly influenced by external fields, geometric phase, and quantum interference effects. Novel techniques such as co-expansion of the colliding species in a supersonic molecular beam (intra-beam scattering) combined with the Stark-induced adiabatic Raman Passage (SARP) allow cold stereochemistry with molecules like H2 and HD initially prepared in a specific or a coherent superposition of magnetic projection quantum numbers, opening up an entirely new regime of cold controlled chemistry without using external trapping fields. Since the experiments lack energy resolution, explicit calculations of energy resolved scattering amplitudes are crucial to provide mechanistic insights into the collision dynamics. The proposed studies include HCl+HD and CO+HD collisions in full six-dimensions and atom-molecule chemical reactions with vibrationally and rotationally excited molecules prepared using the SARP method. The proposed studies may additionally reveal how stereodynamic preparation and non-adiabatic quantum interference effects influence reactivity in cold and ultracold collisions. The project will train a postdoc, provide opportunities for students from traditionally underrepresented communities to engage in STEM related research, and contribute to future workforce development. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.