Magnetic Resonance Force Microscopy: The Quest for a Molecular Structure Microscope

Our work on magnetic resonance force microscopy (MRFM) is motivated by the challenge of three-dimensional molecular imaging at the atomic scale. I will give a brief review of single electron spin detection by MRFM and then describe recent experiments detecting small ensembles of nuclear spins. Using new magnetic tips that generate magnetic field gradients as high as 15 gauss per nanometer, we have achieved a sensitivity on the order of 500 nuclear spins. Rudimentary two-dimensional imaging with spatial resolution on the order of 90 nm has also been achieved. The considerable challenges remaining to achieve single nucleus sensitivity will be discussed.