Underlining the exceptional control possessed by modern chemists, scientists have now trapped two single atoms - cesium and sodium - in individual “optical tweezers” and then guided them together, leading to the formation of a single molecule of sodium cesium (NaCs) with distinctive characteristics.
The methods used for isolating precisely two atoms in this manner, to form a single molecule, could allow the analysis of more varied and more complicated molecules, in isolation, and also enable the preparation of designer molecules that can be used in quantum information applications. In general, when chemists carry out reactions, they combine several reacting partners hoping that they will productively collide.
Atoms can be more deliberately manipulated than this by using a scanning tunneling microscope tip; however, even this process will have limitations. Earlier studies striving to more exquisitely manipulate atoms with the aim of achieving more specific chemical reactions have realized a chemical reaction with a single atomic ion immersed in a gas containing many atoms.
However, in this study, Lee Liu and colleagues endeavored to realize a reaction starting from only two atoms. In order to achieve this, a laser-cooled atom of sodium was held in an optical tweezer of one wavelength, and a laser-cooled atom of cesium was held in an optical tweezer of different wavelength.
Next, a light pulse was used to maneuver the individual laser-cooled atoms (where laser cooling was vital for quantum applications) into a single NaCs molecule, which presented an excited state. According to the authors, when this molecule was analyzed using spectroscopy, it exhibited characteristics which were not observed in NaCs earlier.
Their strategy has opened the door for the analysis of collisions between molecules and atoms in the “cleanest” environment possible.