Periodic Reporting for period 1 - QuantMol (Ultracold polyatomic molecules for controlled chemistry and precision physics)
Reporting period: 2022-10-01 to 2025-03-31
Spectacular successes have already been achieved in quantum simulations of many-body problems and precision measurements with ultracold atoms. Molecules possess a richer internal structure and long-range anisotropic intermolecular interactions, promising a plethora of novel, exciting applications. However, only relatively simple, primarily diatomic molecules have been produced and employed in groundbreaking experiments at ultralow temperatures. When considering combinations of known atoms, there are more than ten thousand possible diatomic molecules, while the number of possible triatomic combinations exceeds one million and the number of isomers of four-atomic molecules -- one billion. The extraordinary variety of polyatomic molecules promises their fascinating properties and applications, prompting the search for new systems suitable for ultracold chemistry and physics experiments. Unfortunately, the complexity of polyatomic molecules has limited the straightforward application of standard atomic techniques of cooling, trapping, and manipulating such molecules. Significant theoretical and computational developments are required to bridge this gap.
In this project, we aim to understand and harness the increasing complexity of ultracold polyatomic molecules to probe the fundamentals of chemistry and physics. We will propose and theoretically investigate new systems, new ways of producing, controlling, and manipulating, and new applications of ultracold polyatomic molecules ranging from controlled chemical reactions to precision measurements. Thus we will extend the range of systems and quantum phenomena ready at hand to be produced and employed in the experiment. Specifically, we will extend the range of polyatomic molecules and their applications by proposing and theoretically investigating in detail two main research paths: 1) association of ultracold deeply-bound diatomic molecules into ultracold weakly-bound polyatomic molecules and 2) direct cooling deeply-bound polyatomic molecules carefully selected and manipulated with electromagnetic fields. Next, we will study new applications exploiting features emerging from single-molecule and coherent control, conical intersections, and non-trivial electronic states and geometries absent in simpler systems. Applications will range from quantum-controlled chemical reactions and molecular dynamics to precision measurements of fundamental constants and their spatio-temporal variation.
The realization of the project will push cold chemistry into the quantum realm and bring unprecedented complexity to ultracold physics, thus, give new insights into the physical basis of chemistry and the fundamental laws of nature. This interdisciplinary project intimately combines the chemistry and physics of ultracold matter. Physical chemistry methods suitably address the molecular complexity, which is at the heart of this proposal. However, relevant experimental realizations are substantially based on methods of ultracold atomic physics and quantum optics.
In this project, we aim to understand and harness the increasing complexity of ultracold polyatomic molecules to probe the fundamentals of chemistry and physics. We will propose and theoretically investigate new systems, new ways of producing, controlling, and manipulating, and new applications of ultracold polyatomic molecules ranging from controlled chemical reactions to precision measurements. Thus we will extend the range of systems and quantum phenomena ready at hand to be produced and employed in the experiment. Specifically, we will extend the range of polyatomic molecules and their applications by proposing and theoretically investigating in detail two main research paths: 1) association of ultracold deeply-bound diatomic molecules into ultracold weakly-bound polyatomic molecules and 2) direct cooling deeply-bound polyatomic molecules carefully selected and manipulated with electromagnetic fields. Next, we will study new applications exploiting features emerging from single-molecule and coherent control, conical intersections, and non-trivial electronic states and geometries absent in simpler systems. Applications will range from quantum-controlled chemical reactions and molecular dynamics to precision measurements of fundamental constants and their spatio-temporal variation.
The realization of the project will push cold chemistry into the quantum realm and bring unprecedented complexity to ultracold physics, thus, give new insights into the physical basis of chemistry and the fundamental laws of nature. This interdisciplinary project intimately combines the chemistry and physics of ultracold matter. Physical chemistry methods suitably address the molecular complexity, which is at the heart of this proposal. However, relevant experimental realizations are substantially based on methods of ultracold atomic physics and quantum optics.
We have already studied intermolecular interactions in several molecule-molecule and atom-molecule systems, with monomers in the ground and excited electronic states. Calculated potential energy surfaces and different fine and hyperfine parameters have been employed in quantum scattering and rovibrational calculations. All the work has aimed to understand and guide the formation and application of ultracold triatomic and tetratomic molecules. Combinations of laser-coolable molecules such as AlF, CaF, and SrOH with laser-coolable atoms such as Rb and Yb have been investigated.
The most important results involve interactions and collisions in AlF+He, AlF+Rb, and AlF+AlF mixtures, where prospects for buffer-gas cooling, Feshbach resonances, and evaporative cooling were studied, respectively. Subtle spin couplings in KRb+Rb were investigated and explained in collaboration with an experimental group. The association of CaF+Yb and CaF+Rb into CaFYb and CaFRb was studied to guide forthcoming experiments. Chemical reactivity and collisional stability for several diatomic molecules were investigated. Optical excitation and stabilization of ultracold field-linked tetratomic molecules was explored as a first step for STIRAP to their absolute ground state.
The suitability and sensitivity of ultracold CaFYb molecules and AcSH+ AcNH2+ molecular ions for probing parity and time-reversal violations occurring in physics beyond the Standard Model were studied. A new class of high-spin sigma-state polar molecules was proposed for a new generation of eEDM experiments.
The most important results involve interactions and collisions in AlF+He, AlF+Rb, and AlF+AlF mixtures, where prospects for buffer-gas cooling, Feshbach resonances, and evaporative cooling were studied, respectively. Subtle spin couplings in KRb+Rb were investigated and explained in collaboration with an experimental group. The association of CaF+Yb and CaF+Rb into CaFYb and CaFRb was studied to guide forthcoming experiments. Chemical reactivity and collisional stability for several diatomic molecules were investigated. Optical excitation and stabilization of ultracold field-linked tetratomic molecules was explored as a first step for STIRAP to their absolute ground state.
The suitability and sensitivity of ultracold CaFYb molecules and AcSH+ AcNH2+ molecular ions for probing parity and time-reversal violations occurring in physics beyond the Standard Model were studied. A new class of high-spin sigma-state polar molecules was proposed for a new generation of eEDM experiments.
Part of the results have been obtained in close collaborations with experimental groups in the EU, USA, and Israel. They intend to explain the performed measurements (e.g. for KRb+Rb), guide the planned experiments (e.g. for CaF+Rb, CaF+Yb), or propose completely new measurements (e.g. for YbCr and field-linked tetramers). The close collaboration with leading experimental groups will continue and enable the implemation of the theoretical results of the project.
Overall, the project has already provided a thorough understanding of the ultracold triatomic and tetratomic mixtures and corresponding molecules, paving the way for the formation and application of ultracold deeply bound polyatomic molecules. The extensive electronic structure calculations from the first years of the project will be employed to guide the use of STIRAP (Stimulated Raman Adiabatic Passage) for transferring weakly bound molecules into stable states and applying them for probing physics beyond the Standard Model in the second part of the project.
Overall, the project has already provided a thorough understanding of the ultracold triatomic and tetratomic mixtures and corresponding molecules, paving the way for the formation and application of ultracold deeply bound polyatomic molecules. The extensive electronic structure calculations from the first years of the project will be employed to guide the use of STIRAP (Stimulated Raman Adiabatic Passage) for transferring weakly bound molecules into stable states and applying them for probing physics beyond the Standard Model in the second part of the project.