Ionizing atoms with a nanotube

Launched laser-cooled atoms are captured by a single, suspended, single-walled carbon nanotube charged to hundreds of volts. A captured atom spirals toward the nanotube (white path) and reaches the environs of the tube surface, where its valence electron (yellow) tunnels into the tube. The resulting ion (purple) is ejected and detected, and the dynamics at the nanoscale are sensitively probed.

In a paper written and published by graduate students Anne Goodsell and Trygve Ristroph, with Professors Lene Hau and Jene Golovchenko, Harvard University, the researchers report the first experimental realization of a combined cold atom-nanostructure system that represents a new paradigm at the interface of these two disciplines. Atoms are laser cooled to microkelvin temperatures and then launched towards a single, freely suspended carbon nanotube charged to hundreds of volts. The nanotube acts as a 'black hole.' Atoms are attracted to the nanotube from distances of more than a hundred times the tube diameter, and spiral towards the tube under dramatic acceleration, with orbit times reaching just a few picoseconds. Close to the nanotube, an atom's valence electron tunnels into the tube, converting the atom into an ion that is ejected at high energy and easily detected. The system demonstrates sensitive probing of atom, electron and ion dynamics at the nanoscale, and opens the door to a new generation of cold atom experiments and nanoscale devices.