During a chemical reaction, large numbers of atoms or molecules move and collide randomly, which occasionally results in a chemical transformation. Researchers trying to control and study chemical reactions on the level of individual atoms or molecules have manipulated individual atoms using a scanning tunneling microscopy (STM) tip. However, these experiments take place on a surface, which influences the results. Studying individual atoms in isolation, in contrast, could improve the understanding of reactions in the gas phase.
Kang-Kuen Ni, Harvard University and Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA, and colleagues have combined two individual atoms (Na and Cs) into a molecule without the help of a surface. The team first prepared laser-cooled sodium and cesium atoms in a vacuum chamber at temperatures as low as several hundred microkelvin and kept them in two overlapping magneto-optical traps (MOTs). Such a trap consists of a laser and a magnetic field which, together, slow down the movement of the trapped particles.
The researchers used “optical tweezers” to manipulate individual atoms. This method uses a focused laser beam to attract or repulse microscopic objects and, thus, move them. Lasers with different wavelengths allowed the researchers to move Na and Cs atoms independently.
The team moved one Na and one Cs atom together. Then they used light to initiate a reaction and form an excited NaCs molecule. The process was monitored using single-molecule spectroscopy. According to the researchers, such molecules with high dipole moments could be useful as molecular qubits in quantum computing. Qubits or quantum bits are the quantum computing analogues of the bits used in “normal”, binary computing.
- Building one molecule from a reservoir of two atoms,
L. R. Liu, J. D. Hood, Y. Yu, J. T. Zhang, N. R. Hutzler, T. Rosenband, K.-K. Ni,
Science 2018, 360, 900–903.