Control over the quantum states of atoms and molecules can lead to a fundamentally new understanding of how these particles interact and react. This knowledge has the potential to impact our ability to probe processes in planetary atmospheres and in the interstellar medium. Experimental techniques developed for control and measurement of atoms are now being used to study more and more complex molecules. We study these rich systems at low temperatures, where we can trap and examine their properties for many minutes, as compared to small fractions of a second in standard experiments. Using these cold, trapped molecular ions, we investigate mechanisms of ion-molecule reactions to gain insights into the mechanisms driving these processes.
Control over the quantum states of atoms and molecules can lead to a fundamentally new understanding of how these particles interact and react. This knowledge has the potential to impact our ability to probe processes in planetary atmospheres and in the interstellar medium. Experimental techniques developed for control and measurement of atoms are now being used to study more and more complex molecules. We study these rich systems at low temperatures, where we can trap and examine their properties for many minutes, as compared to small fractions of a second in standard experiments. Using these cold, trapped molecular ions, we investigate mechanisms of ion-molecule reactions to gain insights into the mechanisms driving these processes.
One of the current themes in quantum physics is the creation of cold ( 1 K) molecules to study molecule-molecule, molecule-atom, and molecule-radiation interactions under these novel low-temperature conditions. This book highlights the field of cold trapped molecular ions. In particular, the development of a novel, universal cooling method for charged particles, sympathetic cooling using laser-cooled atoms, together with the experimental and computational techniques required are extensively reviewed. The book also reviews first spectacular applications of the cold ion ensembles produced: the study of the properties of cold non-neutral plasmas, the study of ion-neutral chemical reactions and of photodissociation processes, and high-resolution rotational overtone spectroscopy of cold hydrogen molecular ions with unprecedented spectral resolution. The large potential of this field of research and its possible impact to other fields of physics, chemistry, and biology are highlighted. The book summarizes the main lines of research in cold trapped molecular ion physics, thus, making it useful as an introduction for advanced students and experienced researchers.
The study of chemical reactions between ions and neutral species at very low energies reveals precise informations about the dynamics of collisions and fine details of intermolecular interactions. Here, we report progress towards the development of next- generation experiments for the investigation of cold ion-neutral reactions. First, we present a new ''dynamic" hybrid ion-atom trap which enables the study of collisions with a superior energy resolution accessing a regime in which quantum scattering resonances may become observable. Second, we discuss and numerically characterize the concept and properties of a hybrid trap for cold neutral molecules and molecular ions which paves the way for the study of ion-molecule reactions in the millikelvin regime.
Recent years have seen tremendous progress in research on cold and controlled molecular collisions, both in theory and in experiment. The advent of techniques to prepare cold and ultracold molecules and ions, to store them in optical lattices or in charged quasicristalline structures, and to use them in crossed or merged beam experiments have opened many new possibilities to study the most fundamental aspects of molecular interactions. At the same time, theoretical work has made progress in tackling these problems and accurately describing quantum effects in complex systems, and in proposing viable options to control chemical reactions at ultralow energies. Through tutorials on both the theoretical and experimental aspects of research in cold and ultracold molecular collisions, this book provides advanced undergraduate students, graduate students and researchers with the foundations needed to understand this exciting field.
Quantum-logic techniques for state preparation, manipulation, and non-destructive interrogation are increasingly being adopted for experiments on single molecular ions confined in traps. The ability to control molecular ions on the quantum level via a co-trapped atomic ion offers intriguing possibilities for new experiments in the realms of precision spectroscopy, quantum information processing, cold chemistry, and quantum technologies with molecules. The present article gives an overview of the basic experimental methods, recent developments and prospects in this field.
This dissertation focuses on observing and controlling cold atom-ion collisions. Such collisions have numerous applications ranging from providing insight into the formation of the interstellar medium to presenting a potential platform for developing quantum information architectures. The experimental apparatus at the center of this work is a hybrid atom-ion trapping system in which laser-cooled Ca atoms held within a magneto-optical trap are spatially overlapped with ions localized within an ion trap. The ions studied in this work are both laser-cooled atomic ions as well as sympathetically cooled molecular ions. As detailed in the remainder of this thesis, by employing tools such as optical pumping, collision energy control, and mass spectrometry, reactions between these species can not only be studied with high precision but can also be controlled, leading to expanded tools for reaction engineering as well as the creation of exotic chemical species. Finally, this work also includes efforts to use inelastic collisions between room temperature BaCl^+} molecular ions and cold Ca atoms to create ro-vibrational ground state molecules, a precursor for developing a high-fidelity qubit based on rotational levels in polar molecules.
Studying chemical reactions at very low temperatures is of importance for the understanding of fundamental physical and chemical processes. At very low energies, collisions are dominated by only a few partial waves. Thus, studies in this regime allow the characterization of quantum effects which depend on the collisional angular momentum, e.g., reactive scattering resonances and tunneling through centrifugal barriers. Additionally, the dynamics of ultralow-energy collisions is dominated by long-range interactions, i.e., “universal” chemical forces. Thus, experiments in this domain probe the details of intermolecular interactions which is of general relevance for the understanding of chemical processes. Moreover, the increasingly more precise experiments provide valuable data for benchmarking theoretical models and quantum chemical calculations. Studies of cold ion–neutral reactions in the laboratory rely on techniques for the generation of cold ions and cold neutrals. Over the last decades, the technology in this domain has made impressive progress. Many of these techniques allow not only the translational cooling of the molecules, but also a precise preparation of their internal quantum state. Thus, by an accurate preparation of both the energy and state of the reaction partners as well as by the application of external electric, magnetic or optical fields, prospects open up to study and control chemical processes at an unprecedented level of accuracy. In this chapter, we review salient theoretical concepts and recent experimental developments for studies of ion–molecule reactions at low temperatures. We first discuss the theoretical background for the description of low-energy ion–molecule reactions. Next we present key experimental methods for laboratory studies of cold ion–molecule reactions. The chapter concludes with a review of illustrative results and an outlook on future directions.