1. A dual-trap design and its applications in electrospray ionization FTICR mass spectrometry
M V Gorshkov, L Pasa-Tolić, J E Bruce, G A Anderson, R D Smith Anal Chem. 1997 Apr 1;69(7):1307-14. doi: 10.1021/ac960941n.
A new arrangement consisting of two separate Fourier transform ion cyclotron resonance (FTICR) ion traps was used to develop methods for the manipulation of the ions produced by an electrospray ionization source (ESI). A first, "accumulation" trap, is generally maintained at a higher pressure than the second, high-performance "analyzer" trap. The manipulations developed and demonstrated include the following: (1) mass-selective ion transfers between the traps; (2) mass-selective step-wise accumulation of low-abundance ions of different mass-to-charge ratios transferred from the first trap to the analyzer trap; (3) simultaneous detection of ions in the analyzer trap and ion accumulation in the source trap; (4) simultaneous ion detection in the accumulation trap and ion storage in the analyzer trap; (5) sequential multiple transfers of the ions into the analyzer trap from the same ion population stored in the accumulation trap; (6) collision-induced dissociation of ions stored in the accumulation trap followed by mass-selective transfer of the product ions into the analyzer trap; (7) sequential transfer of the ions of different mass-to-charge ratios into the analyzer trap from the same ion population stored in the accumulation trap followed by the collision-induced dissociation of transferred ions in the analyzer trap. These ion manipulations benefit multistage studies and are projected to be useful in many biochemical applications of ESI-FTICR, including structural determination of biopolymers and study of noncovalent complexes.
2. Design and characterization of a resonant microwave cavity as a diagnostic for ultracold plasmas
M A W van Ninhuijs, K A Daamen, J Beckers, O J Luiten Rev Sci Instrum. 2021 Jan 1;92(1):013506. doi: 10.1063/5.0037846.
We present the design and commissioning of a resonant microwave cavity as a novel diagnostic for the study of ultracold plasmas. This diagnostic is based on the measurements of the shift in the resonance frequency of the cavity, induced by an ultracold plasma that is created from a laser-cooled gas inside. This method is simultaneously non-destructive, very fast (nanosecond temporal resolution), highly sensitive, and applicable to all ultracold plasmas. To create an ultracold plasma, we implement a compact magneto-optical trap based on a diffraction grating chip inside a 5 GHz resonant microwave cavity. We are able to laser cool and trap (7.25 ± 0.03) × 107 rubidium atoms inside the cavity, which are turned into an ultracold plasma by two-step pulsed (nanosecond or femtosecond) photo-ionization. We present a detailed characterization of the cavity, and we demonstrate how it can be used as a fast and sensitive probe to monitor the evolution of ultracold plasmas non-destructively. The temporal resolution of the diagnostic is determined by measuring the delayed frequency shift following femtosecond photo-ionization. We find a response time of 18 ± 2 ns, which agrees well with the value determined from the cavity quality factor and resonance frequency.
3. Observation of Feshbach resonances between a single ion and ultracold atoms
Pascal Weckesser, Fabian Thielemann, Dariusz Wiater, Agata Wojciechowska, Leon Karpa, Krzysztof Jachymski, Michał Tomza, Thomas Walker, Tobias Schaetz Nature. 2021 Dec;600(7889):429-433. doi: 10.1038/s41586-021-04112-y. Epub 2021 Dec 15.
The control of physical systems and their dynamics on the level of individual quanta underpins both fundamental science and quantum technologies. Trapped atomic and molecular systems, neutral1 and charged2, are at the forefront of quantum science. Their extraordinary level of control is evidenced by numerous applications in quantum information processing3,4 and quantum metrology5,6. Studies of the long-range interactions between these systems when combined in a hybrid atom-ion trap7,8 have led to landmark results9-19. However, reaching the ultracold regime-where quantum mechanics dominates the interaction, for example, giving access to controllable scattering resonances20,21-has so far been elusive. Here we demonstrate Feshbach resonances between ions and atoms, using magnetically tunable interactions between 138Ba+ ions and 6Li atoms. We tune the experimental parameters to probe different interaction processes-first, enhancing three-body reactions22,23 and the related losses to identify the resonances and then making two-body interactions dominant to investigate the ion's sympathetic cooling19 in the ultracold atomic bath. Our results provide deeper insights into atom-ion interactions, giving access to complex many-body systems24-27 and applications in experimental quantum simulation28-30.
