Quantum state control of molecular ions is promising in hybrid ion-atom trap

Hybrid ion-atom traps are a good platform for performing precision measurements of quantum state-dependent interactions. Combined with a time of flight mass spectrometer, the hybrid trap provides improved accuracy in detecting cold reaction products. A recent paper by Jyothi et al. describes a new hybrid ion-atom trap that is coupled with a time of flight mass spectrometer (TOFMS), which allows scientists to explore interactions previously not accessible.

By co-trapping hot atomic or molecular ions with laser-cooled ions, the long-range nature of the Coulomb interaction allows for efficient sympathetic cooling of the hot ions, demonstrated by an about 10-fold improvement in line width and mass resolution. Additionally, the hybrid trap allowed the researchers to observe charge exchange collision interactions between potassium and calcium ions for the first time, the details of which will be revealed in a later publication.

To achieve this, the scientists spatially overlapped a linear quadrupole ion trap and a magneto-optical trap (MOT). By tuning the voltages applied to the ion trap and the magnetic field center of the MOT, the overlap between the atoms and the ions can be optimized. Additionally, the researchers mounted a TOFMS perpendicular to the ion trap axis to identify the reaction products and guided the ions towards it using an electric field gradient.

“Rich chemical reactions between a variety of molecular ions and potassium atoms can be investigated in the system,” said author Saraladevi Jyothi.

Potential future applications of the system include sympathetically cooling molecular ions to their internal ground state for investigating time variations of the proton to electron mass ratio and identifying spectral lines in interstellar clouds.

Source: “A hybrid ion-atom trap with integrated high resolution mass spectrometer,” by S. Jyothi, Kisra N. Egodapitiya, Brad Bondurant, Zhubing Jia, Eric Pretzch, Piero Chiappina, Gang Shu, and Kenneth R. Brown, Review of Scientific Instruments (2019). The article can be accessed at https://doi.org/10.1063/1.5121431 .